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FastMCP 4.x bundles MCP SDK v2, which renamed the ToolAnnotations hint fields from camelCase (readOnlyHint, ...) to snake_case (read_only_hint, ...). The old camelCase attributes still exist but raise a deprecation error on access, so the instrumentation was reading .readOnlyHint, raising, getting swallowed by the try/except in on_call_tool, and silently dropping all read_only/idempotent/external/destructive tags. Add a version-agnostic _annotation_hint() helper that reads snake_case first, falls back to camelCase, and guards every access so a renamed or removed field can never raise out of the instrumentation. Works for dict- and object/pydantic-model-style annotations across FastMCP 2.x/3.x (camelCase) and 4.x (snake_case). Extend the unit tests to cover both camelCase and snake_case object annotations. Verified: full fastmcp test suite passes under fastmcp 2.14.7, 3.4.7, and 4.0.3, plus an end-to-end 4.x app with ScoutMiddleware. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
flake8 6.0.0 bundles an old pyflakes that crashes on Python 3.12+ with
"module ast has no attribute Str" (ast.Str was removed), breaking the
pre-commit CI check on all recent Python. Bump flake8 to 7.3.0
(pyflakes 3.4.0), which is 3.12/3.13/3.14 safe.
flake8 7.x surfaces two pre-existing violations the old pin missed:
* rq.py: remove two unused `global installed` declarations (F824;
the name is only read in those scopes, never assigned).
* tests/.../test_commands.py: rewrite `type(a) == type(b)` as
`isinstance(a, type(b))` (E721).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Fix FastMCP tool annotation tags under FastMCP 4.x (MCP SDK v2)
Problem
CI (and any app on the latest FastMCP) stopped capturing the tool behavioral
annotation tags —
read_only/idempotent/external/destructive.tests/integration/test_fastmcp.py::test_tool_with_metadatafails:Root cause
tox.inipinsfastmcp>=2.9.0with no upper bound, so CI now resolvesFastMCP 4.x, which bundles MCP SDK v2. v2 renamed the
ToolAnnotationshint fields from camelCase to snake_case (
readOnlyHint→read_only_hint,etc.). The old camelCase attributes still exist (
hasattrisTrue) butraise a deprecation error when accessed:
The instrumentation read
annotations.readOnlyHint, which raised, got swallowedby the
try/exceptinon_call_tool, and silently dropped every annotationtag (not just returning wrong values — none at all).
Fix
Add a version-agnostic
_annotation_hint()helper that reads snake_casefirst, then falls back to camelCase, handling both dict- and object/pydantic-
model-style annotations, and guards every access so a renamed/removed field
can never raise out of the instrumentation. This keeps FastMCP 2.x/3.x
(camelCase) working and fixes 4.x (snake_case).
Verification (live, all three majors)
fastmcp 2.14.7— full fastmcp suite 16/16 passfastmcp 3.4.7— 16/16 passfastmcp 4.0.3— reproduced the failure, then 16/16 pass after the fixScoutMiddlewarecalls an annotatedtool → no exception, and
read_only/idempotent/externalare capturedcorrectly.
Unit tests extended to cover both camelCase (2.x/3.x) and snake_case (4.x)
object annotations, with
spec'd mocks so this can't silently drift again.Note: this is independent of the
ca_certwork; it fixes the pre-existing CIfailure on
mastercaused by FastMCP 4.x.