Single tool 'search_username' has acceptable naming and a basic description, but critical gaps in parameter documentation and output schema definition. The tool implementation shows good error handling logic internally, but this is not reflected in the tool schema itself. Missing: parameter descriptions in schema, documented output schema, pagination support, result limits, and structured output documentation. The description is adequate (60 chars) but lacks guidance on when to use the tool or what constraints apply. Input schema is present but minimal, only one parameter with a generic description and no constraints. No enum, pattern, or format constraints. Output is documented only in the Python docstring (not visible to MCP clients), not in the tool schema.

• Add explicit 'returns' documentation to the tool schema. Define output as a structured object with fields: { found: array<{site: string, url: string, exists: boolean}>, total_found: number, error?: string }. Specify the maximum length of the 'found' array.
• Update parameter 'username' description to: 'The username to search for (1-32 alphanumeric characters, letters/numbers/underscores only). Searches across 400+ social media platforms. Note: search may take 10-300 seconds depending on platform availability.'
• Add result limit guidance: 'Returns up to 100 matching profiles. No pagination supported, all results returned in a single call.'
• Enhance tool description to include: 'Requires Sherlock CLI installed. Timeout is 300 seconds per search. Call this when you have a username and need to find associated social media accounts. Returns matching URLs and platform names.'
• Add input validation constraints to the schema: set minimum length 1, maximum length 32 for username. Consider adding a regex pattern (e.g., '^[a-zA-Z0-9_-]+$') to reject invalid characters before calling Sherlock.
• Document error cases in the tool description: 'If Sherlock is not installed, returns error with installation instructions. If search times out after 300 seconds, returns timeout error. If username contains invalid characters, returns validation error.'
• Consider adding an optional 'timeout_seconds' parameter (default 300, range 10-600) to allow callers to tune the search duration.
• Add tool annotation: mark as READ_ONLY (already declared in the server metadata, but ensure it's propagated to the MCP tool schema via readOnlyHint if supported by FastMCP).