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

Annotations only supply destructiveHint=true; the description adds substantive context beyond that: that the operation moves money, that it settles an authorized amount, that partial captures are supported, and the underlying endpoint (POST /payments/{id}/captures). It does not discuss reversibility or failure/idempotency behavior, but the money-movement warning is genuinely valuable.

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?

A single tight sentence with the highest-stakes fact (moves money) front-loaded via emphasis, followed by the endpoint. Zero filler.

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 five-parameter mutation with no output schema, the description conveys the critical facts: it is a settlement operation on a prior authorization with partial support. It omits any note on reversibility or what the capture response yields, but the schema covers all inputs and no output schema exists to explain.

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 description coverage is 100%, so id, amount, metadata, reference, and idempotency_key are already documented in the schema. The description only echoes the full-vs-partial amount concept, adding no syntax or format detail beyond what the schema provides. Baseline 3 applies.

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 (CAPTURES) and resource (previously authorized payment) with the exact effect spelled out: it settles the full or partial authorized amount. This clearly separates it from sibling mutators like checkout_void_payment and checkout_refund_payment without needing to open a 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?

The phrase 'previously authorized payment' implies the precondition for use, which is useful. However, it names no alternatives and gives no when-not guidance — an agent must infer on its own why it would capture rather than void or refund. Implied usage only.

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