Good tool definitions with clear naming, comprehensive schemas, and detailed parameter descriptions. Strong composability for marketplace search workflows. Main gaps: missing error handling guidance for write operations (send_message, place_bid, favorites), no tool annotations (readOnlyHint, destructiveHint, idempotentHint), and output schemas not formally documented in code. Read-only tools (11/19) are well-designed; account/write tools (8/19) lack recovery guidance and confirmation patterns despite having 'confirm' parameters.

• Add readOnlyHint, destructiveHint, and idempotentHint annotations to all tool definitions. Use FastMCP's built-in support for these fields (e.g., via tool.metadata or similar).
• Document output schemas for all tools. Either add return type hints to tool functions or create a schema map (e.g., tool_name → {field: type, ...}) in the registry.
• For write operations, add error recovery guidance to descriptions: 'If the message is rejected due to spam filters, try shortening it or waiting a few minutes before retry. Use get_conversation to verify delivery.'
• Add explicit min/max constraints to pagination parameters: 'limit: 1-100 (default 20)', 'offset: 0 or greater'.
• Enrich error responses from write operations with actionable next steps. E.g., 'Bid rejected: your bid is too low. Current highest bid is €150. Try again with a higher amount.'
• For account tools, clarify authentication in tool descriptions: 'Requires active login session. Pass session credentials via X-Session-Token header.' Verify credentials are NOT in tool parameters.
• Consider adding a 'dry_run' or 'preview' mode to place_bid and send_message for non-destructive testing before confirmation.
• Add batch variants for tools called in loops (e.g., save_favorites accepting a list of listing_ids instead of one at a time).