Split the monolithic Client class into focused mixin classes:
- ClientToolsMixin (tools_client.py)
- ClientPromptsMixin (prompts.py)
- ClientResourcesMixin (resources.py)
- ClientTaskManagementMixin (task_management.py)
Also:
- Extract timeout normalization helpers to utilities/timeout.py
- Split SSETransport into its own module (transports/sse.py)
- Clean up unused imports across client modules
- Fix bare except clauses to catch specific McpError
Note: ty reports unresolved-attribute errors on mixin classes because
it doesn't understand that mixins will be composed with Client. This is
a known limitation of mixin typing in Python. The code is functionally
correct and all tests pass.
Change version parameter from str to VersionSpec in enable()/disable()
to support range-based version filtering.
- Add match_none parameter to VersionSpec.matches() for controlling
whether unversioned components match (defaults to True for backward
compatibility, False for enable/disable filtering)
- Update Enabled transform to use VersionSpec and call matches() with
match_none=False so unversioned components don't match version specs
- Update enable()/disable() signatures to accept VersionSpec
- Add comprehensive tests for version range matching
Examples:
- disable(version=VersionSpec(eq="v2")) - disable only v2
- disable(version=VersionSpec(gte="v2")) - disable v2 and later
- disable(version=VersionSpec(gte="v1", lt="v3")) - disable v1, v2
Rename Visibility to Enabled, collapse VisibilityRule into the transform,
and move enabled filtering from Provider to Server level so server-level
transforms can override provider-level disables.
Server authors opt-in by setting list_page_size on FastMCP.
Client convenience methods auto-fetch all pages transparently.
Use _mcp methods with cursor parameter for manual pagination.
FastMCPProvider now calls _get_* methods instead of get_* to ensure
nested server transforms are applied during lookups. Also converts
string versions to VersionSpec in MCP handlers.
- get_*() now does aggregation + component auth (raises AuthorizationError)
- Deleted _get_*() overrides - inherited from Provider applies transforms
- Simplified AuthMiddleware to global auth only
- Changed version params to VersionSpec | None (not str | None)
- Updated tests to use _get_*() where visibility filtering is expected
Replace _get_all_transforms() with a .transforms property that returns
[*self._transforms, self._visibility]. This cleanly separates user transforms
from visibility filtering while keeping visibility applied last (outermost).
Also:
- AuthMiddleware now uses get_* instead of _get_* for proper component auth
- Remove redundant _is_component_enabled checks (visibility is a transform)
- Delete dead code (get_component method)
- Add versions field to FastMCPMeta
- Replace asserts with NotFoundError in component_service
- Add None checks in auth and tool transform tests
- Add assertions in component_service.py for None returns
- Add type ignore comments for max() with version_sort_key
- Override _get_tool/resource/template/prompt in FastMCP to apply
server transforms over provider aggregation
- Update FastMCPProvider get_* methods to check for None (not
NotFoundError since get_* now returns None)
- Update versioning tests to expect None instead of NotFoundError
when requesting filtered/nonexistent versions
Resolved conflicts to combine Provider inheritance refactor with versioning feature:
- FastMCP now properly inherits from Provider
- get_tool/resource/template/prompt return None instead of raising NotFoundError
- Deduplication uses version_sort_key to keep highest version per name/URI
- _source_* methods eliminated in favor of inherited _* methods
FastMCP now properly inherits from Provider, eliminating ~200 lines of
duplicated _source_* methods. Key changes:
- get_tool/resource/prompt return None instead of raising NotFoundError
- Visibility filter separated from transforms (applied last)
- Nested server middleware runs on both list and execution operations
- Resource auth failure doesn't fall back to templates
- AggregateProvider kept as user-facing utility class
Updates FastMCP's telemetry to align with the new MCP semantic conventions
from open-telemetry/semantic-conventions#2083. This gives us interoperability
with other MCP implementations while keeping fastmcp.* attributes for things
unique to our framework.
Changes:
- Span names now follow `{method} {target}` format (e.g., `tools/call greet`)
- Added `mcp.method.name` and `mcp.resource.uri` attributes
- Renamed `fastmcp.session.id` to standard `mcp.session.id`
- Kept fastmcp.* attributes for server name, component info, provider details
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
- Fix potential None session_id in span attributes
- Add return type annotation to _get_parent_trace_context
- Fix type checker issue with ClientFactoryT await pattern
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds opt-in distributed tracing via OpenTelemetry for observability into
FastMCP server and client operations.
Server spans are created for tool calls, resource reads, and prompt
renders with attributes like component key, component type, provider
type, session ID, and auth context. Client spans wrap outgoing calls
with trace context propagation via W3C headers in request meta.
Components provide their own span attributes through a `get_span_attributes()`
method that subclasses override - this lets LocalProvider, FastMCPProvider,
and ProxyProvider each include relevant context (original names, backend URIs).
To enable: configure an OpenTelemetry SDK with a TracerProvider before
importing fastmcp. Traces export to any OTLP-compatible backend.
Closes ENG-2813
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Tasks belong in capabilities.tasks (first-class field) per SEP-1686,
not capabilities.experimental.tasks. This fixes VS Code Copilot 1.107+
integration which checks capabilities.tasks?.requests?.tools?.call.
Changes:
- Update get_task_capabilities() to return ServerTasksCapability types
- Override get_capabilities() in LowLevelServer to set tasks field
- Remove experimental_capabilities parameter usage
- Update test to verify correct location
Fixes#2870
* Consolidate tool transformation logic into TransformingProvider
Tool transformations were previously scattered across LocalProvider,
ProxyProvider, and MCPConfig. This consolidates all transformation
logic into TransformingProvider via with_transforms(tool_transforms={...}).
- Add tool_transforms parameter to TransformingProvider
- Add tool_transforms to Provider.with_transforms()
- Remove transformation storage from LocalProvider and ProxyProvider
- Remove add_tool_transformation() and remove_tool_transformation() from FastMCP
- Add tool_transforms parameter to factory methods (from_openapi, from_fastapi, create_proxy)
- Update tests to use new patterns
* Fix: reject tool lookups by pre-transform name
* Add collision validation for tool_transforms and fix docstring examples
- Validate duplicate target names in tool_transforms raise ValueError
- Fix docstring examples to use arguments/ArgTransformConfig (not args/ArgTransform)
- Add test for collision validation
* Add server-level tool transform APIs and fix task registration
- Add AggregateProvider to present multiple providers as one
- Add _get_root_provider() to apply server-level transforms uniformly
- Fix _docket_lifespan to use root provider (ensures renamed tools
register with correct keys for background execution)
- Add tool_transforms kwarg to __init__ (non-deprecated)
- Add add_tool_transform(), remove_tool_transform(), tool_transforms property
- Deprecate old API names (tool_transformations, add_tool_transformation, etc.)
- Update tests to use new API
* Add graceful degradation for provider errors in AggregateProvider
* Match original behavior: parallel queries with DEBUG logging
* Refactor transforms to middleware-style call_next pattern
Replaces the ad-hoc transformation system with a unified Transform
abstraction using the same call_next pattern as server middleware.
Key changes:
- New src/fastmcp/server/transforms/ module with Transform base class
- Namespace, ToolTransform, Visibility all implement the same interface
- Transforms compose via functools.partial chain building
- Visibility is now just the first transform in provider._transforms
- Server-level transforms apply after provider aggregation
- Task registration now applies full transform chain
Removes TransformingProvider, _BoundTransform, ComponentSource protocol.
User-facing API unchanged: mount(), add_transform(), enable/disable all
work as before.
* Add comprehensive transforms and visibility documentation
New docs/servers/providers/transforms.mdx covering:
- Mental model for middleware-style transform pattern
- Built-in transforms (Namespace, ToolTransform)
- Server vs provider-level transforms and ordering
- Tool modification (immediate vs deferred)
- Custom transform creation
New docs/servers/visibility.mdx covering:
- Enable/disable API for runtime visibility control
- Keys and tags for targeting components
- Allowlist mode with only=True
- Server vs provider visibility layering
Updates existing docs to reference new pages and simplifies
redundant content. Visibility is documented as a user feature,
not as an implementation detail.
* Restructure transforms docs and delete tool-transformation pattern
* Cleanup: simplify get_tasks and remove unused Provider.get_component
* Update loq
* Update loq limits and add loq note to AGENTS.md
* Deprecate add_tool_transformation and tool_transformations param
* Address PR review feedback: remove redundant imports, fix path reference
* Add missing imports to code examples in v3-features.mdx
