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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description goes further by disclosing the seller-scoped authorization ('for the authenticated seller'), the exact 404 behavior on a missing ID, and the test-mode-vs-live record distinction, all genuine behavioral context 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?

Front-loaded with the core operation, then routing guidance, then failure/behavior notes, then concrete examples. The read-only statement is partly redundant with readOnlyHint but is a short, high-value reinforcement for a retrieval tool rather than padding.

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?

An output schema exists, so return-value explanation is rightly omitted. For a single-record getter, the description covers purpose, routing to siblings, auth scoping, error behavior, and mode switching — nothing an agent needs to call it correctly is missing.

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 both parameters (paymentId, livemode) are already fully documented in the schema, which sets the baseline at 3. The description restates the livemode:false test-mode behavior and the ID-discovery hint, adding reinforcement but no syntax or format details the schema lacks.

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 and resource ('Retrieve a single payment by ID') and immediately scopes it to the Checkout Page account. It explicitly distinguishes itself from the record types an agent might confuse it with (bookings vs. payments), which is exactly the differentiation needed among 50+ siblings.

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 names the alternatives and the conditions selecting them: use `list_payments` first to discover an ID by email/name/product/order, and use `list_bookings` for event bookings. It even states the failure mode (404 'Payment not found') and where mutations must happen instead (the dashboard).

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