`codeql_bqrs_decode`: singular `file` argument is rejected; tool requires `files` (array)

[data-douser]

Summary

The codeql_bqrs_decode MCP tool rejects a singular file argument with a validation error and instead requires files (an array). This is confusing and inconsistent: the server's internal tool registry / parameter handling references a singular file parameter for the BQRS tools, but the exposed MCP input schema requires the plural files. Callers (including LLM clients) naturally try file first and hit a hard error.

Steps to reproduce

1. Invoke codeql_bqrs_decode with a singular file argument, e.g.:

   { "file": "/path/to/results.bqrs", "format": "csv" }

2. Observe the validation error:

   Input validation error: Invalid arguments for tool codeql_bqrs_decode: must have required property 'files'
   

3. Re-invoke with the plural array form, which succeeds:

   { "files": ["/path/to/results.bqrs"], "format": "csv" }

Expected

A consistent, discoverable input contract. Either:

• accept a singular file (a single BQRS path is the common case), or
• treat files as canonical but accept file as an alias / normalize file → files, or
• at minimum, produce an error that names the correct parameter and shows the expected shape.

Likely area

There is a mismatch between the internal handling of BQRS tools (which references a singular file) and the input schema actually advertised over MCP (which requires files). The parameter-name normalization that already maps camelCase/snake_case variants for other tools does not bridge file ↔ files here.

Suggested direction

• Align the advertised input schema with the registry's handling, and/or add file ↔ files normalization so both forms work for the codeql_bqrs_* tools.
• Add a unit test asserting that both a singular file and a files array are accepted (or that the rejection message clearly points at the correct parameter).

Impact

Low functional impact (a workaround exists), but it is a recurring usability papercut and a likely source of failed first attempts by automated/LLM clients.