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

Beyond the annotations, the description discloses key behavioral traits: an 8-digit code is emailed with no link, the code expires in 30 minutes, there is a rate limit of three starts per email per day, and the key starts read-only. These details are crucial for correct invocation and are not present in the structured 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 dense but front-loaded with the endpoint and purpose, and every sentence carries useful behavioral or sequencing information. It could be slightly more structured (e.g., with bullet points), but it is appropriately sized for the tool's complexity.

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 no output schema and rich behavioral requirements, the description covers the initiation step, rate limits, email behavior, kind-specific requirements, and the explicit next step. An agent has enough information to call the tool and proceed to signup_confirm without ambiguity.

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?

Despite only 44% schema coverage, the description clarifies the most consequential parameters: it explains the kind enum (warehouse, seller, buyer), notes that a buyer's company is optional and no address is asked, and specifies that a warehouse provides a street address. It does not cover city, state, sqft, or services, but it compensates well for the critical conditional requirements.

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 states a specific verb (POST /signup/start) and resource (open a CommerceBook account), and it distinguishes the step from the sibling signup_confirm by describing the flow. An agent can tell exactly what this tool initiates.

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?

It provides clear sequencing ('Then ask the owner for the code and call signup_confirm') and explains the kind choices, but it does not explicitly state when not to use the tool (e.g., if an account already exists). The usage context is clear, though not exhaustive.

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