feat(security-agent-mcp-server): Add custom User-Agent

[jigar-lab]

Summary

Adds a custom User-Agent string to all boto3 API calls from the security-agent-mcp-server, enabling service-side tracking of MCP usage by IDE/tool.

User-Agent format

md/awslabs#mcp#security-agent-mcp-server#0.1.2 md/client#kiro/1.5.0

Follows the repo-wide md/awslabs#mcp#<server-name>#<version> convention, with an additional md/client#<name>/<version> suffix for IDE tracking.

How it works

1. aws_client.py: SecurityAgentClient builds a botocore.config.Config(user_agent_extra=...) and passes it to every .client() call (securityagent, sts, s3, iam). Uses the package __version__ constant directly.
2. server.py: @ensure_client_ua decorator extracts clientInfo from the MCP session context (sent by the IDE during initialize) and calls set_mcp_client_info() on the shared AWS client singleton.

Design decisions

• __version__ constant: Uses the package-level __version__ instead of importlib.metadata.version() to avoid silent degradation to "unknown" in editable/source installs.
• Sanitized client name: clientInfo.name is normalized with .lower().replace(" ", "-") before injection into the UA string, preventing malformed tokens (e.g. "Claude Code" → "claude-code").
• Decorator pattern: @ensure_client_ua applied to all tool functions as a single choke point — no per-tool boilerplate, and new tools cannot forget it.
• Lazy injection: The SecurityAgentClient singleton is created at module level before any MCP session connects, so clientInfo is injected on first tool invocation.
• No-op optimization: set_mcp_client_info() short-circuits if the info has not changed.
• Graceful fallback: Falls back to unknown when clientInfo is unavailable.
• Concurrency note: Current stdio transport guarantees one client per process. Under future HTTP/SSE transport with concurrent sessions, _config would need per-session isolation.

Tracking values by IDE

IDE	md/client# value
Kiro	kiro/<version>
Claude Code	claude-code/<version>
Cursor	cursor/<version>
Unknown	unknown

Tested

• All 41 unit tests pass (197 total including existing)
• E2E verified: API call to SecurityAgent service confirmed the custom UA on the wire
• Works with Kiro, Claude Code, and any MCP-compliant client that sends clientInfo

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By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.13%. Comparing base (1ea4990) to head (f815bc6).
✅ All tests successful. No failed tests found.

Additional details and impacted files

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##             main    #4319   +/-   ##
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  Coverage   93.12%   93.13%           
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  Files        1036     1036           
  Lines       87307    87358   +51     
  Branches    14085    14090    +5     
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+ Hits        81308    81359   +51     
  Misses       3638     3638           
  Partials     2361     2361           

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[scottschreckengaust]

Thanks for adding usage telemetry — the lazy-injection approach is reasonable and every failure path degrades gracefully (no crashes). I reviewed at high effort and verified the technical claims below empirically. Two items keep the PR from delivering its own stated contract and are worth fixing before merge; the rest are cleanup/altitude.

Should fix (contract gaps):

1. get_api_guide sends an untagged User-Agent. It builds its own session.client('securityagent') without config=, so it's the one .client() site the PR didn't thread the custom UA through — contradicting "passes it to every .client() call." The _ensure_client_ua(ctx) at the top of that tool is also inert, since it mutates the _client singleton this tool bypasses.
2. Version reports unknown from any uninstalled/editable checkout. importlib.metadata.version('awslabs.security-agent-mcp-server') raises PackageNotFoundError when run from source (verified in this repo), silently degrading to unknown. __version__ = '0.1.2' is already exported by __init__.py, and ~30 other servers in this repo build the UA from that constant. Reusing it also removes the per-rebuild metadata lookup.

Consider (cleanup / consistency):
3. clientInfo.name is injected into the UA unsanitized, unlike _client_prefix which normalizes it — a name like Claude Code produces a broken UA token (botocore does not sanitize user_agent_extra; confirmed).
4. _ensure_client_ua(ctx) is duplicated as the first line of all 11 tools, and duplicates the clientInfo-extraction logic already in _client_prefix (with a divergent fallback: unknown vs ide).
5. The shared mutable _client._config is safe under today's stdio transport but would cross-contaminate the UA across concurrent sessions under HTTP/SSE.

Inline comments below. Nothing here is a crash; posting as a Comment, not a blocking Request Changes.