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

The `readOnlyHint: true` annotation already indicates this is a read-only operation. The description adds the HTTP method (GET) and path, but does not disclose additional behavioral traits such as error handling, rate limits, or response format beyond the annotation.

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 extremely concise: two short sentences, no filler, and front-loaded with the essential purpose. Every sentence earns its place.

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 simple get-by-ID tool with one parameter and annotations covering safety, the description is minimally adequate. However, since there is no output schema, a brief note on the response shape (e.g., 'returns the transaction object') would improve completeness for agents.

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% with a single parameter `transactionId` described as 'Transaction ID.' The description adds no extra meaning beyond the schema's description, so baseline score of 3 is appropriate.

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 'Get a single payment transaction by ID', specifying the action (get), resource (single transaction), and the required ID. This distinguishes it from sibling tools like `mercoa_find_transactions` which is for searching multiple transactions.

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 when you have a transaction ID and need the single transaction details, but it does not explicitly state when to use this tool versus alternatives like `mercoa_find_transactions`. No when-not or alternative tool names are mentioned.

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