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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description goes well beyond them: it discloses the timeout return shape ({timed_out: true, cursor}), the 4,000-char extracted_text cap, the specific failure modes (404 inbox_not_found, 400 invalid_cursor), and flags the body as untrusted data.

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 usage then the parameter list and return/failure behavior; every sentence carries information. It is dense and slightly long, but nothing reads as filler.

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?

With no output schema, the description fully specifies the success return (message.received summary, extracted_text, attachments, cursor) and the timeout return, plus error cases. An agent has everything needed to call and interpret it.

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 coverage is already 100%, so parameters are documented structurally. The description adds genuine meaning beyond the schema, notably that 'after' defaults to the time of this call so only later-arriving mail matches, and that matching is case-insensitive substring on From/subject.

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+resource (wait for a message) and immediately scopes it to the no-webhook case, distinguishing it from the sibling cooper_wait_for_code and from webhook tools. An agent can tell what this does without opening the 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 states when to use it ('waiting for a reply or a verification code and you have no public URL for a webhook'), effectively naming the alternative (webhooks) and the exclusion condition. Nothing is left to inference.

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