…or unquoted parameters (googleapis#3273)

## Description

LookML `parameter` fields declared `type: unquoted` reject queries
through the Looker tools because filter values arrive with a literal
layer of wrapping quote characters and are substituted into SQL bare via
`{% parameter %}` — producing invalid SQL like `... = "first_touch"`.

`ProcessQueryArgs` in
`internal/tools/looker/lookercommon/lookercommon.go` already strips a
wrapping layer of quotes from filter *keys*; this extends the same
handling to string *values*, stripping a single layer of wrapping `"` or
`'` only when the first and last characters match. Bare values are
correct for all parameter types over the `WriteQuery` wire format, so
this is applied unconditionally — no need to branch on the field's
declared LookML type. The `filters` parameter description is also
tightened so the model is told explicitly not to wrap values in extra
quotes, addressing the upstream cause while the normalization stays a
backstop.

One fix covers every tool built on the shared helper: `looker-query`,
`looker-query-sql`, `looker-query-url`, `looker-make-look`, and
`looker-add-dashboard-element`.

## Tests

- **Unit:** added `TestProcessQueryArgsStripsWrappingQuotes` exercising
`ProcessQueryArgs` directly — bare values (unchanged), double-quoted
values, single-quoted values, quoted keys (regression),
quoted-key+quoted-value, non-string values (untouched), single-character
strings (no length-check footgun), and mismatched wrapping characters
(left alone). `go test -race ./internal/tools/looker/lookercommon/...`
passes.
- **Integration:** updated the `filters` manifest assertions in
`tests/looker/looker_integration_test.go` to match the tightened
parameter description, keeping the live
`looker-query`/`looker-query-sql`/`looker-query-url` integration suite
green.

## PR Checklist

- [x] Make sure you reviewed
[CONTRIBUTING.md](https://github.com/googleapis/mcp-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a bug/issue before writing your
code!
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change

🛠️ Fixes googleapis#3272

Co-authored-by: Dr. Strangelove <drstrangelove@google.com> 1e3de96

🤖 I have created a release *beep* *boop*
---


##
[1.3.0](v1.2.0...v1.3.0)
(2026-05-21)


### Features

* **auth:** Implement MCP auth tool-level scopes validation
([#3049](#3049))
([c528985](c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([#3253](#3253))
([75da6c2](75da6c2))
* Setup SQLCommenter and allow client metadata
([#3064](#3064))
([9f1f9b3](9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([#3083](#3083))
([ef300a8](ef300a8))


### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([#3251](#3251))
([f4d16c0](f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([#3036](#3036))
([c739b80](c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([#3218](#3218))
([80a6602](80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([#3233](#3233))
([4f409a3](4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([#3273](#3273))
([1e3de96](1e3de96))
* **tools:** Initialize query result slices to empty array
([#3250](#3250))
([60ddf48](60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com>

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([#3049](#3049))
([c528985](c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([#3253](#3253))
([75da6c2](75da6c2))
* Setup SQLCommenter and allow client metadata
([#3064](#3064))
([9f1f9b3](9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([#3083](#3083))
([ef300a8](ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([#3251](#3251))
([f4d16c0](f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([#3036](#3036))
([c739b80](c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([#3218](#3218))
([80a6602](80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([#3233](#3233))
([4f409a3](4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([#3273](#3273))
([1e3de96](1e3de96))
* **tools:** Initialize query result slices to empty array
([#3250](#3250))
([60ddf48](60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

🤖 I have created a release *beep* *boop*
---

##
[1.3.0](googleapis/mcp-toolbox@v1.2.0...v1.3.0)
(2026-05-21)

### Features

* **auth:** Implement MCP auth tool-level scopes validation
([googleapis#3049](googleapis#3049))
([c528985](googleapis@c528985))
* **looker:** Propagate client IP from incoming MCP requests to
downstream SDK calls
([googleapis#3253](googleapis#3253))
([75da6c2](googleapis@75da6c2))
* Setup SQLCommenter and allow client metadata
([googleapis#3064](googleapis#3064))
([9f1f9b3](googleapis@9f1f9b3))
* **tool/cloudsqladmin:** Add `cloud-sql-admin-execute-sql-many` and
`cloud-sql-admin-sql-many`
([googleapis#3083](googleapis#3083))
([ef300a8](googleapis@ef300a8))

### Bug Fixes

* **auth/generic:** Fix generic auth expiration field and integration
with `authRequired`
([googleapis#3251](googleapis#3251))
([f4d16c0](googleapis@f4d16c0))
* Enforce toolset/promptset boundary on tools/call and prompts/get
([googleapis#3036](googleapis#3036))
([c739b80](googleapis@c739b80))
* **tools/http:** Prevent path traversal and base path scope escape
([googleapis#3218](googleapis#3218))
([80a6602](googleapis@80a6602))
* **tools/looker:** Return a 401 error to MCP client when Looker returns
a 401 ([googleapis#3233](googleapis#3233))
([4f409a3](googleapis@4f409a3))
* **tools/looker:** Strip wrapping quotes from filter values for
unquoted parameters
([googleapis#3273](googleapis#3273))
([1e3de96](googleapis@1e3de96))
* **tools:** Initialize query result slices to empty array
([googleapis#3250](googleapis#3250))
([60ddf48](googleapis@60ddf48))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Yuan Teoh <45984206+Yuan325@users.noreply.github.com> b001006

## Description

PR #3273 fixed the wrapping-quote case for `type: unquoted` Looker
parameter filters, but the value still reaches Looker un-escaped, so
identifiers containing `_`, `%`, or `,` are still rejected by Looker's
filter-expression parser. The parser treats `_` as a single-character
wildcard and `%` as a multi-character wildcard; for `type: unquoted`
parameters the substituted SQL must match `[A-Za-z0-9_.$]` literally, so
`first_touch` is expanded into a wildcard pattern and 400s with `The
filter "first_touch" is not allowed.` Looker's own
`default_filter_value` is stored already escaped (`first^_touch`),
confirming that filter-expression escape is the correct wire format for
`/queries/run`.

This adds a new helper `EscapeUnquotedParameterFilters` in
`internal/tools/looker/lookercommon/lookercommon.go` that fetches the
explore's parameter metadata via `sdk.LookmlModelExplore` and escapes
`^`/`_`/`%`/`,` with a `^` prefix in any string filter value keyed to a
`type: unquoted` parameter. `ProcessQueryArgs` stays pure and keeps the
wrapping-quote stripping from #3273. The new helper is idempotent —
values that already contain `^` are assumed pre-escaped and pass through
unchanged — so callers can keep using the raw `default_filter_value`
form. Metadata-lookup failures degrade to a no-op so users without
explore-read permission still get their non-parameter queries through.

Wired into every WriteQuery-building tool: `looker-query`,
`looker-query-sql`, `looker-query-url`, `looker-make-look`, and
`looker-add-dashboard-element`.

## Tests

- **Unit:** added `TestEscapeFiltersForUnquotedParameters` and
`TestEscapeFiltersForUnquotedParameters_NoopGuards` in
`internal/tools/looker/lookercommon/lookercommon_test.go` covering:
single-metacharacter escape, multi-metacharacter escape in one value,
pre-escaped pass-through, no-metacharacter pass-through, non-parameter
filters untouched, non-string values untouched, mixed filters, empty
unquoted set is a no-op, and nil-guard panics. `go test -race
./internal/tools/looker/...` passes.
- **End-to-end:** verified against the live Looker API — posting
`{"…attribution_model_selector": "first_touch"}` to `/queries/run/json`
400s with the documented error; the same body after the escape
(`first^_touch` on the wire) returns rows.

## PR Checklist

- [x] Make sure you reviewed
[CONTRIBUTING.md](https://github.com/googleapis/mcp-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a bug/issue before writing your
code!
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #3288

---------

Co-authored-by: Dr. Strangelove <drstrangelove@google.com>