search_messages

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and destructiveHint=false, indicating safety. The description adds valuable behavioral context: results never expose raw unsubscribe URLs or message bodies, and the search operates on cached headers. This exceeds annotation coverage and provides critical privacy/security assurances.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences with no wasted words. It front-loads the core purpose, then explains query behavior, and finally lists filters and result limitations. Every sentence adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no output schema and 15 parameters, the description is reasonably complete but lacks details about the return format (e.g., which header fields are included) and pagination behavior (limit/offset). The result limitation is mentioned, but for a search tool, more context on output structure would be beneficial.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate. It explains that the free-text query matches subject, sender domain, and sender email, and lists additional exact filters (account, folder, sender, date, unsubscribe, decision) which map to several parameters. However, it does not explain parameters like sort, limit, offset, include_sender_email, exclude_stale, or subject_contains, leaving gaps.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool searches cached message headers without connecting to IMAP, which distinguishes it from potentially similar tools that require IMAP connectivity. The verb 'search' and resource 'cached message headers' are specific and unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use this tool (for offline, cached search) by stating 'without connecting to IMAP'. However, it does not explicitly state when not to use it or mention alternative sibling tools, though the context helps inform decision-making.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.