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

Annotations declare it is a non-destructive, idempotent, openWorld write, but the description adds behavior they cannot convey: a human (Bill) manually verifies availability and price, replies by email typically within a day, the request is free, and the tool 'can't buy or reserve the number.' That limitation and the cost/timeline disclosure are exactly the context an agent needs before promising anything to a user.

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 action and its condition, then the human-review/timeline/cost expectations and the explicit limitation. Every sentence earns its place, though the opening sentence is dense and slightly hard to parse on first read.

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 still notes it 'returns whether it was sent and what happens next.' Combined with the caveat that it cannot buy or reserve, an agent has everything needed to call and set expectations.

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 100%, so the schema already documents name, email, number, and the optional message. The description reinforces the identity of the 'number' (vendor-held, no list price) but adds no format, validation, or mapping detail beyond what the schema supplies. Baseline 3 is appropriate when the schema carries the parameter burden.

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 ('Pass along a person's request for a toll free number held by another vanity number vendor') and disambiguates the resource by tying it to what 'check_number and the searches show as with another vendor, with no list price.' An agent can distinguish this from the sibling search/check tools 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?

Gives an explicit trigger: 'Use it when the person asks to request that number and gives their name and email.' It also implicitly routes away from check_number and the search tools by naming them as the tools that surface vendor-held numbers rather than acting on them.

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