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

readOnlyHint=true already declares the safety profile, and the description adds useful context: this is a single-record fetch keyed by the global ID via the `node` query, returning id, legacyId, name, company, and created-at. It does not mention auth requirements or rate limits, but for a read-only single lookup the disclosure is solid.

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 tight sentences: the lookup semantics and return shape come first, then the sibling routing. No filler and nothing repeated from the title.

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?

With no output schema, the description usefully lists the returned fields, and with only one fully-documented parameter and a read-only annotation, nothing an agent needs to call this 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 coverage is 100% and the single parameter already documents that the id is an opaque GraphQL global ID with a note about legacy numeric ids. The description only restates 'GraphQL global Customer ID' without adding format, syntax, or resolution detail beyond the schema, so the 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 and resource ('Fetch one customer') plus the exact lookup mechanism ('GraphQL global Customer ID via the `node` query') and enumerates the returned fields. It also names the sibling tool it is not, so an agent can distinguish it from braintree_customer_payment_methods without opening either 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?

Explicitly routes the agent: use braintree_customer_payment_methods when you also need stored cards/PayPal accounts. This gives a clear alternative with a selecting condition, though it doesn't state when the tool should NOT be used (e.g., for legacy numeric ids, which is only covered in the schema).

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