search_emails

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It discloses the output format ('Returns message summaries with message_ref fields') and the filter requirement, but it does not explicitly state that the operation is read-only or describe ordering/pagination behavior. This is a minor gap for a search tool, but not fully transparent.

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 two sentences, front-loaded with the core purpose, and contains no redundancy. Every sentence adds essential information: what the tool does, what it returns, and a key usage constraint.

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?

For a 7-parameter tool with no output schema, the description covers the essential aspects: purpose, filter requirement, scope, and output type. It does not mention ordering or pagination, but the schema already documents the limit parameter. The message_ref mention provides integration context, though it could be more explicit about return value structure.

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 100%, so the baseline is 3. The description adds value by grouping filters and emphasizing the 'at least one filter' constraint, which is not explicitly stated in the schema. This guides correct invocation beyond individual parameter descriptions.

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's function: 'Search for emails matching criteria across one or all mailboxes.' It uses a specific verb and resource, and distinguishes itself from siblings by noting it returns message summaries with message_ref fields for use with other tools, which sets it apart from list_emails and get_email.

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 usage context by stating 'At least one filter (from_filter, subject_filter, after_date, before_date) should be provided.' This implies the tool is for filtered searches, but it does not explicitly name alternatives or when not to use it, leaving some room for ambiguity versus list_emails.

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