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

Annotations already carry readOnly/openWorld/non-destructive, so the description only needs to add context — and it does: it discloses the returned data set and the Cotlet API key access requirement. It does not mention error behavior for a missing/invalid client_id, keeping it short of a 5.

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?

Three sentences, front-loaded with the resource, then the returned fields, then the use case and auth note — no filler. The opening 'One client with all fiscal data and email addresses' slightly overlaps the more precise second sentence, but overall it is tight.

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?

No output schema exists, yet the description compensates by enumerating the returned fields, and it flags the auth requirement. For a single-parameter read tool this is nearly complete; only failure/not-found behavior is unaddressed.

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 param already documents its source ('Client ID from list_clients or create_client'), so the description adds no syntax, format, or validation detail beyond that. Baseline 3 is appropriate when the schema fully carries the parameter.

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+resource (retrieve one client) and enumerates the exact fiscal fields returned (RFC, name, CFDI use, tax zip code, fiscal regime, email). It implies the singular-vs-list distinction against facturama_list_clients but never names that sibling explicitly, so differentiation is inferable rather than stated.

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?

Gives a concrete when-to-use: verify a client has every field a CFDI 4.0 invoice requires before stamping. That is real usage context, but there is no when-not guidance and no alternative named (e.g., prefer list_clients when you don't have an ID).

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