Add support for MCP tools/list_changed notification#42453
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agu-z merged 5 commits intozed-industries:mainfrom Dec 16, 2025
Merged
Add support for MCP tools/list_changed notification#42453agu-z merged 5 commits intozed-industries:mainfrom
agu-z merged 5 commits intozed-industries:mainfrom
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This commit adds support for the MCP (Model Context Protocol) notifications/tools/list_changed notification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools. Changes: - Register a notification handler for 'notifications/tools/list_changed' in ContextServerRegistry - Automatically reload tools when the notification is received - Handler is registered both on initial server startup and when a server transitions to Running status This allows the Zed agent to dynamically discover and use new tools from MCP servers without requiring a server restart, improving the developer experience and enabling more flexible tool management.
Collaborator
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Hey @tsoernes, thank you for this! I'm not so familiar with this – would you be able to share more context / screenshots for how this is done in e.g. Cursor or VS Code or similar? 🙏 |
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Contributor
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@tsoernes Thank you for your contribution! The changes look good overall. I did notice that the existing MCP client didn’t have a way to unregister notification handlers, which meant they could leak when a new agent instance was created. This is now handled by tying the handler’s lifetime to the registry, which is itself scoped to the agent’s lifetime. |
HactarCE
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Dec 17, 2025
## Summary This PR adds support for the MCP (Model Context Protocol) `notifications/tools/list_changed` notification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools at runtime. ## Release Notes: - Improved: MCP tools are now automatically reloaded when a context server sends a `tools/list_changed` notification, eliminating the need to restart the server to discover new tools. ## Changes - Register a notification handler for `notifications/tools/list_changed` in `ContextServerRegistry` - Automatically reload tools when the notification is received - Handler is registered both on initial server startup and when a server transitions to `Running` status ## Motivation The MCP specification includes a `notifications/tools/list_changed` notification to inform clients when the list of available tools has changed. Previously, Zed's agent would only load tools once when a context server started. This meant that: 1. If an MCP server dynamically registered new tools after initialization, they would not be available to the agent 2. The only way to refresh tools was to restart the entire context server 3. Tools that were removed or modified would remain in the old state until restart ## Implementation Details The implementation follows these steps: 1. When a context server transitions to `Running` status, register a notification handler for `notifications/tools/list_changed` 2. The handler captures a weak reference to the `ContextServerRegistry` entity 3. When the notification is received, spawn a task that calls `reload_tools_for_server` with the server ID 4. The existing `reload_tools_for_server` method handles fetching the updated tool list and notifying observers This approach is minimal and reuses existing tool-loading infrastructure. ## Testing - [x] Code compiles with `./script/clippy -p agent` - The notification handler infrastructure already exists and is tested in the codebase - The `reload_tools_for_server` method is already tested and working ## Benefits - Improves developer experience by enabling hot-reloading of MCP tools - Aligns with the MCP specification's capability negotiation system - No breaking changes to existing functionality - Enables more flexible and dynamic MCP server implementations ## Related Issues This implements part of the MCP specification that was already defined in the type system but not wired up to actually handle the notifications. --------- Co-authored-by: Agus Zubiaga <agus@zed.dev>
LivioGama
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Jan 20, 2026
…2453) ## Summary This PR adds support for the MCP (Model Context Protocol) `notifications/tools/list_changed` notification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools at runtime. ## Release Notes: - Improved: MCP tools are now automatically reloaded when a context server sends a `tools/list_changed` notification, eliminating the need to restart the server to discover new tools. ## Changes - Register a notification handler for `notifications/tools/list_changed` in `ContextServerRegistry` - Automatically reload tools when the notification is received - Handler is registered both on initial server startup and when a server transitions to `Running` status ## Motivation The MCP specification includes a `notifications/tools/list_changed` notification to inform clients when the list of available tools has changed. Previously, Zed's agent would only load tools once when a context server started. This meant that: 1. If an MCP server dynamically registered new tools after initialization, they would not be available to the agent 2. The only way to refresh tools was to restart the entire context server 3. Tools that were removed or modified would remain in the old state until restart ## Implementation Details The implementation follows these steps: 1. When a context server transitions to `Running` status, register a notification handler for `notifications/tools/list_changed` 2. The handler captures a weak reference to the `ContextServerRegistry` entity 3. When the notification is received, spawn a task that calls `reload_tools_for_server` with the server ID 4. The existing `reload_tools_for_server` method handles fetching the updated tool list and notifying observers This approach is minimal and reuses existing tool-loading infrastructure. ## Testing - [x] Code compiles with `./script/clippy -p agent` - The notification handler infrastructure already exists and is tested in the codebase - The `reload_tools_for_server` method is already tested and working ## Benefits - Improves developer experience by enabling hot-reloading of MCP tools - Aligns with the MCP specification's capability negotiation system - No breaking changes to existing functionality - Enables more flexible and dynamic MCP server implementations ## Related Issues This implements part of the MCP specification that was already defined in the type system but not wired up to actually handle the notifications. --------- Co-authored-by: Agus Zubiaga <agus@zed.dev>
LivioGama
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to LivioGama/zed
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Jan 20, 2026
…2453) ## Summary This PR adds support for the MCP (Model Context Protocol) `notifications/tools/list_changed` notification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools at runtime. ## Release Notes: - Improved: MCP tools are now automatically reloaded when a context server sends a `tools/list_changed` notification, eliminating the need to restart the server to discover new tools. ## Changes - Register a notification handler for `notifications/tools/list_changed` in `ContextServerRegistry` - Automatically reload tools when the notification is received - Handler is registered both on initial server startup and when a server transitions to `Running` status ## Motivation The MCP specification includes a `notifications/tools/list_changed` notification to inform clients when the list of available tools has changed. Previously, Zed's agent would only load tools once when a context server started. This meant that: 1. If an MCP server dynamically registered new tools after initialization, they would not be available to the agent 2. The only way to refresh tools was to restart the entire context server 3. Tools that were removed or modified would remain in the old state until restart ## Implementation Details The implementation follows these steps: 1. When a context server transitions to `Running` status, register a notification handler for `notifications/tools/list_changed` 2. The handler captures a weak reference to the `ContextServerRegistry` entity 3. When the notification is received, spawn a task that calls `reload_tools_for_server` with the server ID 4. The existing `reload_tools_for_server` method handles fetching the updated tool list and notifying observers This approach is minimal and reuses existing tool-loading infrastructure. ## Testing - [x] Code compiles with `./script/clippy -p agent` - The notification handler infrastructure already exists and is tested in the codebase - The `reload_tools_for_server` method is already tested and working ## Benefits - Improves developer experience by enabling hot-reloading of MCP tools - Aligns with the MCP specification's capability negotiation system - No breaking changes to existing functionality - Enables more flexible and dynamic MCP server implementations ## Related Issues This implements part of the MCP specification that was already defined in the type system but not wired up to actually handle the notifications. --------- Co-authored-by: Agus Zubiaga <agus@zed.dev>
LivioGama
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to LivioGama/zed
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Feb 15, 2026
…2453) ## Summary This PR adds support for the MCP (Model Context Protocol) `notifications/tools/list_changed` notification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools at runtime. ## Release Notes: - Improved: MCP tools are now automatically reloaded when a context server sends a `tools/list_changed` notification, eliminating the need to restart the server to discover new tools. ## Changes - Register a notification handler for `notifications/tools/list_changed` in `ContextServerRegistry` - Automatically reload tools when the notification is received - Handler is registered both on initial server startup and when a server transitions to `Running` status ## Motivation The MCP specification includes a `notifications/tools/list_changed` notification to inform clients when the list of available tools has changed. Previously, Zed's agent would only load tools once when a context server started. This meant that: 1. If an MCP server dynamically registered new tools after initialization, they would not be available to the agent 2. The only way to refresh tools was to restart the entire context server 3. Tools that were removed or modified would remain in the old state until restart ## Implementation Details The implementation follows these steps: 1. When a context server transitions to `Running` status, register a notification handler for `notifications/tools/list_changed` 2. The handler captures a weak reference to the `ContextServerRegistry` entity 3. When the notification is received, spawn a task that calls `reload_tools_for_server` with the server ID 4. The existing `reload_tools_for_server` method handles fetching the updated tool list and notifying observers This approach is minimal and reuses existing tool-loading infrastructure. ## Testing - [x] Code compiles with `./script/clippy -p agent` - The notification handler infrastructure already exists and is tested in the codebase - The `reload_tools_for_server` method is already tested and working ## Benefits - Improves developer experience by enabling hot-reloading of MCP tools - Aligns with the MCP specification's capability negotiation system - No breaking changes to existing functionality - Enables more flexible and dynamic MCP server implementations ## Related Issues This implements part of the MCP specification that was already defined in the type system but not wired up to actually handle the notifications. --------- Co-authored-by: Agus Zubiaga <agus@zed.dev>
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Summary
This PR adds support for the MCP (Model Context Protocol)
notifications/tools/list_changednotification, enabling dynamic tool discovery when MCP servers add, remove, or modify their available tools at runtime.Release Notes:
tools/list_changednotification, eliminating the need to restart the server to discover new tools.Changes
notifications/tools/list_changedinContextServerRegistryRunningstatusMotivation
The MCP specification includes a
notifications/tools/list_changednotification to inform clients when the list of available tools has changed. Previously, Zed's agent would only load tools once when a context server started. This meant that:Implementation Details
The implementation follows these steps:
Runningstatus, register a notification handler fornotifications/tools/list_changedContextServerRegistryentityreload_tools_for_serverwith the server IDreload_tools_for_servermethod handles fetching the updated tool list and notifying observersThis approach is minimal and reuses existing tool-loading infrastructure.
Testing
./script/clippy -p agentreload_tools_for_servermethod is already tested and workingBenefits
Related Issues
This implements part of the MCP specification that was already defined in the type system but not wired up to actually handle the notifications.