Improve MCP server: init instructions and helpful database error by robfrank · Pull Request #3966 · ArcadeData/arcadedb

robfrank · 2026-04-23T07:50:06Z

superseds #3896

Summary

Added init instructions to the MCP server so LLMs know to list databases before querying
When a query targets a non-existent database, the error now includes the list of databases the user can access, allowing the LLM to self-correct without a separate list_databases round-trip
Centralized the canAccessToDatabase authorization check inside MCPToolUtils.resolveDatabase, removing duplicated guards from QueryTool, ExecuteCommandTool, and GetSchemaTool
Switched database filtering to removeIf(db -> !user.canAccessToDatabase(db)) for correctness and clarity

Test plan

MCPServerPluginTest covers the new init instructions and the available-databases error message
Verify restricted users who mistype a database name receive the filtered available-databases list rather than a bare SecurityException
Verify unauthorized access to an existing database still throws SecurityException

Move canAccessToDatabase guard into MCPToolUtils.resolveDatabase so all tools benefit consistently and restricted users who mistype a database name get the helpful "available databases" list rather than a bare SecurityException. Also switch to removeIf + canAccessToDatabase for the available-databases filter, dropping the manual wildcard check. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

codacy-production · 2026-04-23T07:51:02Z

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 4 complexity

Metric Results

Complexity 4

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🟢 Coverage 100.00% diff coverage · -8.64% coverage variation

Metric Results

Coverage variation ✅ -8.64% coverage variation

Diff coverage ✅ 100.00% diff coverage

View coverage diff in Codacy

Coverage variation details

Coverable lines Covered lines Coverage

Common ancestor commit (830e38e) 119759 88317 73.75%

Head commit (efc1437) 151000 (+31241) 98310 (+9993) 65.11% (-8.64%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

Coverable lines Covered lines Diff coverage

Pull request (#3966) 11 11 100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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gemini-code-assist

Code Review

This pull request introduces a centralized database resolution utility, MCPToolUtils, which is now used across the ExecuteCommandTool, GetSchemaTool, and QueryTool to handle database existence and permission checks. A key improvement is the inclusion of available database names in the error message when a requested database is not found, allowing LLMs to self-correct. Additionally, the MCPHttpHandler now provides explicit operational instructions to the client, and new tests verify the enhanced error reporting. Feedback was provided to correct a type mismatch in MCPToolUtils where the implementation class ServerDatabase was used instead of the Database interface, which would lead to compilation errors.

gemini-code-assist · 2026-04-23T07:51:54Z

+  public static ServerDatabase resolveDatabase(final ArcadeDBServer server, final ServerSecurityUser user,
+      final String databaseName) {


The return type must be changed to Database. Since ArcadeDBServer.getDatabase() returns the Database interface, returning it as ServerDatabase without an explicit cast will cause a compilation error. Furthermore, all tools calling this method (QueryTool, ExecuteCommandTool, GetSchemaTool) already expect the Database interface.

Suggested change

public static ServerDatabase resolveDatabase(final ArcadeDBServer server, final ServerSecurityUser user,

final String databaseName) {

public static Database resolveDatabase(final ArcadeDBServer server, final ServerSecurityUser user,

final String databaseName) {

gemini-code-assist · 2026-04-23T07:51:54Z

+import java.util.TreeSet;
+
+import com.arcadedb.server.ArcadeDBServer;
+import com.arcadedb.server.ServerDatabase;


The utility should use the Database interface instead of the ServerDatabase implementation. This aligns with the return type of ArcadeDBServer.getDatabase() and the expectations of the calling tools.

Suggested change

import com.arcadedb.server.ServerDatabase;

import com.arcadedb.database.Database;

codecov · 2026-04-23T11:53:38Z

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 64.09%. Comparing base (830e38e) to head (efc1437).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...va/com/arcadedb/server/mcp/tools/MCPToolUtils.java	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3966      +/-   ##
==========================================
- Coverage   64.77%   64.09%   -0.68%     
==========================================
  Files        1596     1597       +1     
  Lines      119759   119761       +2     
  Branches    25470    25468       -2     
==========================================
- Hits        77576    76766     -810     
- Misses      31472    32409     +937     
+ Partials    10711    10586     -125

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…skip ci] Bumps [org.postgresql:postgresql](https://github.com/pgjdbc/pgjdbc) from 42.7.10 to 42.7.11. Release notes *Sourced from [org.postgresql:postgresql's releases](https://github.com/pgjdbc/pgjdbc/releases).* > v42.7.11 > -------- > > Security > -------- > > * fix: Limit SCRAM PBKDF2 iterations accepted from the server. > pgjdbc was vulnerable to a client-side denial of service in SCRAM-SHA-256 authentication, where a malicious or compromised PostgreSQL server could specify an extremely large PBKDF2 iteration count, causing the client to consume unbounded CPU and potentially exhaust connection pools. The fix introduces a new scramMaxIterations connection property (defaulting to 100,000) to cap iteration counts before computation begins. > See the [Security Advisory](GHSA-98qh-xjc8-98pq) for more detail. > The following [CVE-2026-42198](https://nvd.nist.gov/vuln/detail/CVE-2026-42198) has been issued. > > Changes > ------- > > * fix: Add sources and javadocs to shaded published lib generation [`@sehrope`](https://github.com/sehrope) ([#4043](https://redirect.github.com/pgjdbc/pgjdbc/issues/4043)) > * update Changelog and website for release of 42.7.11 [`@davecramer`](https://github.com/davecramer) ([#4042](https://redirect.github.com/pgjdbc/pgjdbc/issues/4042)) > * Fix scram fix location in changelog and update published artifact developer list [`@sehrope`](https://github.com/sehrope) ([#4041](https://redirect.github.com/pgjdbc/pgjdbc/issues/4041)) > * Restrict test with scram\_iterations to v16+ and release notes [`@sehrope`](https://github.com/sehrope) ([#4040](https://redirect.github.com/pgjdbc/pgjdbc/issues/4040)) > * chore(deps): update ubuntu:24.04 docker digest to 84e77de [`@renovate-bot`](https://github.com/renovate-bot) ([#4017](https://redirect.github.com/pgjdbc/pgjdbc/issues/4017)) > * test: add tests for QueryExecutor#getTransactionState [`@vlsi`](https://github.com/vlsi) ([#4006](https://redirect.github.com/pgjdbc/pgjdbc/issues/4006)) > * chore(deps): update actions/create-github-app-token action to v2.2.2 [`@renovate-bot`](https://github.com/renovate-bot) ([#3983](https://redirect.github.com/pgjdbc/pgjdbc/issues/3983)) > * fix: fix flaky CopyBothResponseTest by using WAL flush LSN [`@vlsi`](https://github.com/vlsi) ([#3979](https://redirect.github.com/pgjdbc/pgjdbc/issues/3979)) > * fix: fix flaky replication restart tests by waiting for confirmed\_flush\_lsn [`@vlsi`](https://github.com/vlsi) ([#3975](https://redirect.github.com/pgjdbc/pgjdbc/issues/3975)) > * test: fix flaky LogicalReplicationStatusTest by polling pg\_stat\_replication [`@vlsi`](https://github.com/vlsi) ([#3974](https://redirect.github.com/pgjdbc/pgjdbc/issues/3974)) > * chore: replace Appveyor with ikalnytskyi/action-setup-postgres [`@vlsi`](https://github.com/vlsi) ([#3966](https://redirect.github.com/pgjdbc/pgjdbc/issues/3966)) > * test: move test table creation from [`@BeforeEach`](https://github.com/BeforeEach) to [`@BeforeAll`](https://github.com/BeforeAll) [`@vlsi`](https://github.com/vlsi) ([#3967](https://redirect.github.com/pgjdbc/pgjdbc/issues/3967)) > * Return jsonb as PGObject fixes Issue [#3926](https://redirect.github.com/pgjdbc/pgjdbc/issues/3926) [`@davecramer`](https://github.com/davecramer) ([#3956](https://redirect.github.com/pgjdbc/pgjdbc/issues/3956)) > * Update docker scripts [`@davecramer`](https://github.com/davecramer) ([#3958](https://redirect.github.com/pgjdbc/pgjdbc/issues/3958)) > * implement require\_auth, this is pretty much how libpq does this. [`@davecramer`](https://github.com/davecramer) ([#3895](https://redirect.github.com/pgjdbc/pgjdbc/issues/3895)) > * docs: add SCRAM authentication test setup section to TESTING.md [`@emmaeng700`](https://github.com/emmaeng700) ([#3945](https://redirect.github.com/pgjdbc/pgjdbc/issues/3945)) > * Add RequireServerVersion annotation for tests [`@sehrope`](https://github.com/sehrope) ([#3939](https://redirect.github.com/pgjdbc/pgjdbc/issues/3939)) > > 🐛 Bug Fixes > ----------- > > * fix: ensure extended protocol messages end with Sync message [`@vlsi`](https://github.com/vlsi) ([#3728](https://redirect.github.com/pgjdbc/pgjdbc/issues/3728)) > * fix: enable cursor-based fetching in extended protocol when transaction started via SQL command [`@vlsi`](https://github.com/vlsi) ([#3996](https://redirect.github.com/pgjdbc/pgjdbc/issues/3996)) > * fix: retry with SSL on IOException when sslMode=ALLOW [`@vlsi`](https://github.com/vlsi) ([#3973](https://redirect.github.com/pgjdbc/pgjdbc/issues/3973)) > * fix: allow fallback to non-SSL connection when sslMode=prefer and sslResponseTimeout kicks in [`@vlsi`](https://github.com/vlsi) ([#3968](https://redirect.github.com/pgjdbc/pgjdbc/issues/3968)) > * fix: catch SecurityException from setContextClassLoader on ForkJoinPool workers [`@vlsi`](https://github.com/vlsi) ([#3962](https://redirect.github.com/pgjdbc/pgjdbc/issues/3962)) > * fix: use compareTo for LogSequenceNumber comparison [`@vlsi`](https://github.com/vlsi) ([#3961](https://redirect.github.com/pgjdbc/pgjdbc/issues/3961)) > * fix: release COPY lock on IOException to prevent connection hang ([#3957](https://redirect.github.com/pgjdbc/pgjdbc/issues/3957)) [`@vlsi`](https://github.com/vlsi) ([#3960](https://redirect.github.com/pgjdbc/pgjdbc/issues/3960)) > > 🧰 Maintenance > ------------- > > * style: replace [`@exception`](https://github.com/exception) with [`@throws`](https://github.com/throws) in getBoolean javadoc [`@vlsi`](https://github.com/vlsi) ([#4035](https://redirect.github.com/pgjdbc/pgjdbc/issues/4035)) > * chore: use `@vlsi/github-actions-random-matrix` npm package [`@vlsi`](https://github.com/vlsi) ([#4008](https://redirect.github.com/pgjdbc/pgjdbc/issues/4008)) > * chore: use tag names for pinning github actions, pin ikalnytskyi/action-setup-postgres [`@vlsi`](https://github.com/vlsi) ([#4007](https://redirect.github.com/pgjdbc/pgjdbc/issues/4007)) > * chore: bump errorprone to 2.48.0 [`@vlsi`](https://github.com/vlsi) ([#4005](https://redirect.github.com/pgjdbc/pgjdbc/issues/4005)) > * test: add [`@DisableLogger`](https://github.com/DisableLogger) annotation to suppress expected log warnings in tests [`@vlsi`](https://github.com/vlsi) ([#3971](https://redirect.github.com/pgjdbc/pgjdbc/issues/3971)) > * chore: suppress deprecations in test code to reduce build verbosity [`@vlsi`](https://github.com/vlsi) ([#3972](https://redirect.github.com/pgjdbc/pgjdbc/issues/3972)) > * chore: replace log warning in ConnectionFactory.closeStream with Throwable.addSuppressed [`@vlsi`](https://github.com/vlsi) ([#3970](https://redirect.github.com/pgjdbc/pgjdbc/issues/3970)) > * chore: use greedy pairwise coverage for CI matrix generation [`@vlsi`](https://github.com/vlsi) ([#3965](https://redirect.github.com/pgjdbc/pgjdbc/issues/3965)) > * chore: use full version tags in GitHub Actions comments [`@vlsi`](https://github.com/vlsi) ([#3963](https://redirect.github.com/pgjdbc/pgjdbc/issues/3963)) > > ⬆️ Dependencies > --------------- ... (truncated) Changelog *Sourced from [org.postgresql:postgresql's changelog](https://github.com/pgjdbc/pgjdbc/blob/master/CHANGELOG.md).* > [42.7.11] (2026-04-28) > ---------------------- > > ### Security > > * fix: Limit SCRAM PBKDF2 iterations accepted from the server. > pgjdbc was vulnerable to a client-side denial of service in SCRAM-SHA-256 authentication, where a malicious or compromised PostgreSQL server could specify an extremely large PBKDF2 iteration count, causing the client to consume unbounded CPU and potentially exhaust connection pools. The fix introduces a new scramMaxIterations connection property (defaulting to 100,000) to cap iteration counts before computation begins. > See the [Security Advisory](GHSA-98qh-xjc8-98pq) for more detail. > The following [CVE-2026-42198](https://nvd.nist.gov/vuln/detail/CVE-2026-42198) has been issued. > > ### Added > > * feat: implement require\_auth connection property, aligning with libpq behavior [PR [#3895](https://redirect.github.com/pgjdbc/pgjdbc/issues/3895)]([pgjdbc/pgjdbc#3895](https://redirect.github.com/pgjdbc/pgjdbc/pull/3895)) > > ### Changed > > * chore: replace Appveyor CI with ikalnytskyi/action-setup-postgres [PR [#3966](https://redirect.github.com/pgjdbc/pgjdbc/issues/3966)]([pgjdbc/pgjdbc#3966](https://redirect.github.com/pgjdbc/pgjdbc/pull/3966)) > * chore: upgrade Gradle to v9 [PR [#3978](https://redirect.github.com/pgjdbc/pgjdbc/issues/3978)]([pgjdbc/pgjdbc#3978](https://redirect.github.com/pgjdbc/pgjdbc/pull/3978)) > > ### Fixed > > * fix: ensure extended protocol messages end with Sync message [PR [#3728](https://redirect.github.com/pgjdbc/pgjdbc/issues/3728)]([pgjdbc/pgjdbc#3728](https://redirect.github.com/pgjdbc/pgjdbc/pull/3728)) > * fix: enable cursor-based fetching in extended protocol when transaction started via SQL command [PR [#3996](https://redirect.github.com/pgjdbc/pgjdbc/issues/3996)]([pgjdbc/pgjdbc#3996](https://redirect.github.com/pgjdbc/pgjdbc/pull/3996)) > * fix: retry with SSL on IOException when sslMode=ALLOW [PR [#3973](https://redirect.github.com/pgjdbc/pgjdbc/issues/3973)]([pgjdbc/pgjdbc#3973](https://redirect.github.com/pgjdbc/pgjdbc/pull/3973)) > * fix: make sure the driver honours connectTimeout when retrying the connection [PR [#3968](https://redirect.github.com/pgjdbc/pgjdbc/issues/3968)]([pgjdbc/pgjdbc#3968](https://redirect.github.com/pgjdbc/pgjdbc/pull/3968)) > * fix: allow fallback to non-SSL connection when sslMode=prefer and sslResponseTimeout kicks in [PR [#3968](https://redirect.github.com/pgjdbc/pgjdbc/issues/3968)]([pgjdbc/pgjdbc#3968](https://redirect.github.com/pgjdbc/pgjdbc/pull/3968)) > * fix: catch SecurityException from setContextClassLoader on ForkJoinPool workers [PR [#3962](https://redirect.github.com/pgjdbc/pgjdbc/issues/3962)]([pgjdbc/pgjdbc#3962](https://redirect.github.com/pgjdbc/pgjdbc/pull/3962)) > * fix: use compareTo for LogSequenceNumber comparison to handle unsigned values correctly [PR [#3961](https://redirect.github.com/pgjdbc/pgjdbc/issues/3961)]([pgjdbc/pgjdbc#3961](https://redirect.github.com/pgjdbc/pgjdbc/pull/3961)) > * fix: release COPY lock on IOException to prevent connection hang [PR [#3957](https://redirect.github.com/pgjdbc/pgjdbc/issues/3957)]([pgjdbc/pgjdbc#3957](https://redirect.github.com/pgjdbc/pgjdbc/pull/3957)) > * fix: return jsonb as PGObject instead of String [PR [#3956](https://redirect.github.com/pgjdbc/pgjdbc/issues/3956)]([pgjdbc/pgjdbc#3956](https://redirect.github.com/pgjdbc/pgjdbc/pull/3956)) > * fix: align SSL key file permission check with libpq [PR [#3952](https://redirect.github.com/pgjdbc/pgjdbc/issues/3952)]([pgjdbc/pgjdbc#3952](https://redirect.github.com/pgjdbc/pgjdbc/pull/3952)) > * fix: guard connection closed flag with a reentrant lock to protect against concurrent close [PR [#3905](https://redirect.github.com/pgjdbc/pgjdbc/issues/3905)]([pgjdbc/pgjdbc#3905](https://redirect.github.com/pgjdbc/pgjdbc/pull/3905)) Commits * [`78e261f`](pgjdbc/pgjdbc@78e261f) fix: Add sources and javadocs to shaded published lib generation * [`1e09fa0`](pgjdbc/pgjdbc@1e09fa0) update Changelog and website for release of 42.7.11 ([#4042](https://redirect.github.com/pgjdbc/pgjdbc/issues/4042)) * [`d479fa5`](pgjdbc/pgjdbc@d479fa5) Fix scram fix location in changelog and update published artifact developer l... * [`b04fc46`](pgjdbc/pgjdbc@b04fc46) docs: Add scram max iters fix to changelog * [`cf54822`](pgjdbc/pgjdbc@cf54822) test: Disable scram test on older version without scram\_iterations GUC * [`7dbcc79`](pgjdbc/pgjdbc@7dbcc79) test: Add SCRAM max iteration tests * [`c9d41d1`](pgjdbc/pgjdbc@c9d41d1) fix: Limit SCRAM PBKDF2 iterations accepted from the server * [`a340cb2`](pgjdbc/pgjdbc@a340cb2) style: replace [`@exception`](https://github.com/exception) with [`@throws`](https://github.com/throws) in getBoolean javadoc * [`77837f8`](pgjdbc/pgjdbc@77837f8) fix(deps): update dependency org.openrewrite.rewrite:org.openrewrite.rewrite.... * [`23af03b`](pgjdbc/pgjdbc@23af03b) chore(deps): update actions/checkout action to v6 * Additional commits viewable in [compare view](pgjdbc/pgjdbc@REL42.7.10...REL42.7.11) [![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility\_score?dependency-name=org.postgresql:postgresql&package-manager=maven&previous-version=42.7.10&new-version=42.7.11)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- Dependabot commands and options You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot show ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)

CNE Pierre FICHEPOIL and others added 3 commits April 23, 2026 09:23

improved MCP with available db list on unknown db targeted

520678a

Added init instructuctions in MCP

85e00f8

robfrank added this to the 26.4.1 milestone Apr 23, 2026

gemini-code-assist Bot reviewed Apr 23, 2026

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robfrank merged commit d6bf401 into main Apr 23, 2026
24 of 28 checks passed

robfrank deleted the feat/improve-mcp branch April 23, 2026 07:58

robfrank mentioned this pull request Apr 23, 2026

Improved MCP server with init instructions and server list in query error #3896

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Improve MCP server: init instructions and helpful database error#3966

Improve MCP server: init instructions and helpful database error#3966
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		public static ServerDatabase resolveDatabase(final ArcadeDBServer server, final ServerSecurityUser user,
		final String databaseName) {

	import com.arcadedb.server.ServerDatabase;
	import com.arcadedb.database.Database;

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