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

readOnlyHint=true already tells the agent this is a safe read, so the description only needs to add context. It contributes the underlying REST endpoint (GET /v2/payments/{id}), which is marginal, and says nothing about 404 behavior, auth scope, or whether a missing id returns an error.

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 short sentences, zero filler, with the core action and its lookup keys front-loaded before the endpoint reference. Nothing could be trimmed without losing information.

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-resource getter the description is functional but thin: with no output schema, it gives no hint of what a payment record contains, and it is silent on the failure case (unknown id / bad key). Adequate, not complete.

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 schema description already states 'The payment id or the transaction id.' The description repeats this dual-key behavior rather than adding format, prefix, or resolution-order details, so 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 payment') plus the accepted lookup keys (payment id or transaction id), which implicitly separates it from list_payments. It stops short of naming the sibling explicitly, but the singular scope is unambiguous.

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 mention of 'by payment id or transaction id' implies the precondition for calling it, but there is no explicit when-to-use guidance, no when-not, and no pointer to list_payments as the alternative for browsing.

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