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

Annotations indicate non-read-only and non-idempotent behavior. The description adds crucial context: the key is a one-time return, reinforcing the need for immediate storage. This goes beyond the 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?

Two sentences with clear front-loading: the first sentence explains the action, the second provides critical usage guidance. No extraneous words.

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?

Covers the core action, one-time nature, and storage instruction. Lacks details on what happens if called again (likely error) and no output schema, but the description is sufficient for a simple tool.

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?

With 0% schema coverage, the description compensates by labeling sessionId as the 'paid agent checkout' and claimToken as the 'secret claim token', adding meaning beyond the parameter names.

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 verb 'Exchange' and resources 'paid agent checkout plus its secret claim token for a new API key'. It distinguishes from siblings like create_checkout and checkout_status by specifying the post-payment claim step.

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?

Provides context that the key is returned once and must be stored immediately, warning against repeated calls. However, it does not explicitly list when to use this tool vs alternatives like checkout_status or create_checkout.

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