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

Annotations already indicate readOnlyHint=false (mutation) and destructiveHint=false. The description adds context by explaining that the tool 'appends credit.purchase with credits_added' and that credits become spendable, which is a behavioral disclosure beyond the annotations. It does not mention error conditions or idempotency, but for a test tool this is adequate.

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 two sentences with no filler. The primary action and endpoint are front-loaded, followed by the effect and test-only constraint. Every word contributes to understanding the tool's purpose and scope.

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 test tool with no output schema, the description covers purpose, effect, and test scope. It does not describe response behavior or idempotency, but given the simplicity and existing annotations, the information provided is sufficient for correct invocation.

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?

The schema covers the single parameter with a clear description ('PaymentIntent id (pi_…) from checkout_credits'), so schema coverage is 100%. The description adds minimal extra meaning by referencing the card and endpoint, but does not elaborate on parameter format or sourcing beyond what the schema already states.

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 ('Confirm'), the resource ('a TEST PaymentIntent'), and the specific effect ('credits become granted/spendable'). It also includes the endpoint and the test card used, and specifies it is TEST only, distinguishing it from production operations and other tools like checkout_credits.

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 usage after checkout_credits by referencing 'PaymentIntent id (pi_…) from checkout_credits' in the schema, and states 'TEST only'. It does not explicitly say 'use this after checkout' or provide exclusions, but the context is clear enough for an agent to infer the intended workflow.

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