Search mail messages

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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds genuine behavioral context beyond them: results with a keyword are ordered by relevance rather than date, and each item reports match_field and match_in to explain where a hit landed. It stops short of disclosing pagination or truncation behavior for the limit parameters.

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?

Front-loaded with the purpose and the sibling routing before the syntax details. It is dense and mostly earns its length, though the keyword-syntax sentence is long and the match_field/match_in discussion pushes toward verbosity.

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?

An output schema exists, so return values need not be explained and the description need not cover them. However, with 14 params at 0% schema coverage, the absence of any guidance on the many filters and limit parameters leaves meaningful gaps for correct invocation, even if most names are self-explanatory.

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% across 14 parameters, so the description must compensate. It thoroughly documents the keyword syntax and indirectly ties full_body to summary vs full-body items, but the other 12 parameters (date filters, sender/recipient/domain filters, body_max_chars, recipients_limit, attachments_limit) are left entirely undocumented in both schema and description.

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?

States a specific verb and resource: 'Find message candidates by keyword and structured filters.' It also explicitly routes away from siblings, naming mail_show for a single id and mail_thread for a conversation or Message-ID, so an agent can distinguish this tool without opening any schema.

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?

Explicitly names the alternatives and the conditions that select them: mail_show for one stored id, mail_thread for a whole conversation or an RFC822 Message-ID. The condition that selects search (keyword and structured filters returning candidates) is clear, leaving nothing to inference.

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