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

Annotations already declare read-only, idempotent, and non-destructive. The description adds substantial behavioral detail: 'Saved-data reads only', 'Results are not snapshot-consistent', 'Bound concurrency, honor Retry-After... back off on transient failures', and scope restrictions. It also clarifies that these readers do not enable exterior automation or inside-page extraction beyond already-authorized data. No contradiction with annotations.

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 long but logically organized: search semantics → filters → return type → exclusions → pagination → consistency → rate limits → auth requirements. It is front-loaded with the core purpose and every sentence carries information not already present in the schema or annotations. For a tool with 7 parameters and many behavioral constraints, the length is justified.

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 the output schema exists and the tool's complexity (search semantics, date filtering, pagination limits, scopes, concurrency, error handling), the description covers every invocation-relevant aspect. It even addresses edge cases like empty-search scope requirements and the prohibition on switching keys or accounts. Nothing an agent needs to call it correctly is missing.

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 only 43%, but the description compensates thoroughly. It explains q's literal AND behavior, NFKC/lowercase normalization, 200-character/12-term limits, and cross-page matching. It clarifies received_after/before as inclusive/exclusive intake-time filters, and provides pagination guidance for limit/offset: 'follow pagination.has_more using offset plus returned count'. This prevents ambiguity for undocumented parameters.

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 opens with a specific verb-resource pair: 'Search managed-renter physical mail through GET /v1/inbound-items?search_mode=documents.' It also clarifies what it returns ('item metadata and canonical owner/mailbox identity, not page text') and explicitly directs to a sibling for page sources, which distinguishes it from related tools.

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 explicitly names an alternative ('Use get_inbound_item_sources for selected items') and lists many non-goals ('no extraction, retry, signed image URL, facility action, provider call, email or charge'). It also provides prerequisites (saved-document reads, active managed mailbox, required scopes) and detailed pagination/error-handling guidance, giving an agent clear when-to-use and when-not-to-use context.

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