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 bar is lower. The description adds only the underlying API route (GET /credit_notes/{lago_id}), which gives no behavioral detail such as what a missing id returns or whether the response is cached/paginated.

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, front-loaded with the operation and resource, with the API route as a compact secondary reference. No 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?

There is no output schema, so the description is the only place the return shape could be described, and it says nothing about what a credit note object contains. For a trivial single-resource getter with read-only annotations and complete parameter docs, this is adequate but noticeably thin.

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 required parameter already documented as a UUID in the schema, so the description need not add anything. Its mention of 'Lago id' merely echoes the schema, matching the baseline for fully-covered parameters.

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 ('Retrieve') and resource ('a single credit note') identified by Lago id, which cleanly separates it from the list-style sibling lago_list_credit_notes. It stops short of naming that sibling explicitly, so it misses the top band.

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 'by its Lago id' implies the precondition (you must already have an id), but there is no explicit when-to-use guidance, no statement of when to prefer the list tool instead, and no error/not-found guidance. Usage is inferable but not stated.

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