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

Annotations already indicate this is not read-only and not destructive. The description adds valuable behavioral context: it's a TEST PaymentIntent, it only creates a pending state, credits are not spendable until confirm_credits, and it requires a caller key. This goes beyond the annotations and helps the agent understand side effects and prerequisites.

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 sentences, each earning its place: what it does, the critical pending-state caveat, and the auth requirement. Front-loaded with the core action and endpoint.

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?

For a single-parameter tool with no output schema, the description covers the essential context: the endpoint, the test nature, the pending state, the follow-up tool, and the auth requirement. It doesn't describe the return format, but with no output schema and a simple intent-only operation, this is a minor gap.

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% and the single parameter pack_id is already described as 'Pack id from list_credit_packs (e.g. pack_10).' The description doesn't add much beyond the schema, but the schema is sufficient. Baseline 3 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 specific action (Stripe TEST PaymentIntent for a pack), the endpoint (POST /credits/checkout), and the key behavior (intent only, credits not granted until confirm_credits). It distinguishes itself from confirm_credits by explicitly noting the follow-up 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?

The description implies when to use this tool: to initiate a credit pack purchase, with the explicit note that credits are not granted until confirm_credits succeeds. It names the sibling confirm_credits as the follow-up, but doesn't explicitly state when not to use it or compare with quote_credits. The context is clear enough for an agent to select it correctly.

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