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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. The description adds value by specifying the returned content (version, hash, timestamp) and advising caching and dependency for sync verification. This provides behavioral context beyond what annotations offer, though minor details like error conditions are omitted.

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?

Three well-structured sentences: first states purpose, second details return fields, third gives critical usage guidance. No wasted words; information is front-loaded and dense.

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 zero parameters and presence of an output schema, the description covers all necessary context: what the tool does, what it returns, and how to use its output (caching and passing the version to send_outbound_mail). It fully equips the agent to use the tool correctly.

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?

The tool has zero parameters and schema coverage is 100%, so the baseline is 3. The description does not need to explain parameters; it instead focuses on return values and usage, which is appropriate.

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 retrieves the renter's MAILBOX.md standing instructions, specifies the exact return fields (full instruction text, version number, content hash, last update timestamp), and implicitly distinguishes it from siblings like get_mailbox and propose_mailbox_md_edit by highlighting its specific role in sync verification for send_outbound_mail.

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?

Explicit guidance is given: 'Call this on startup and cache the version — you must pass it to send_outbound_mail for sync verification.' This tells the agent when to use it and how to use the result, but does not explicitly state when not to use it or mention alternatives, though the sibling list provides context.

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