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

Goes well beyond the annotations by disclosing irreversibility ('cannot be undone from here'), the not-found failure mode, the default per-call confirmation (which can be disabled), and the API-key/auth requirement. These are meaningful behavioral traits the structured fields do not convey. The 'cannot be undone' wording sits in mild tension with destructiveHint=false, but is not a true contradiction since the record persists with a new status.

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?

Front-loads the purpose before operational details, and most sentences carry distinct information (irreversibility, error, confirmation, auth). A couple of lines (default confirmation, API-key note) read as platform boilerplate, keeping it from being maximally tight, but there is no significant padding.

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 covers the return shape ('returns its new status'), the failure behavior, the irreversibility of the mutation, and the auth requirement. For a mutation tool with annotations present, this is nearly complete; only explicit alternatives and any rate/permission nuance are 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 description coverage is 100%, so all three parameters are already documented by the schema. The description restates that 'the cancellation reason is the code the SAT asks for' without adding syntax, allowed values, or mapping beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Cancel a stamped invoice or credit note with the SAT') and scopes the operation to a single stamped document. This clearly separates it from siblings like create_invoice, get_invoice, list_invoices, and even facturama_create_credit_note. An agent can identify the tool without opening the 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?

Provides clear operational context: the cancel targets a stamped document, requires an SAT reason code, and fails with not-found when the ID is invalid. However, it never explicitly routes the agent between this tool and alternatives (e.g., issuing a credit note instead of cancelling), so exclusions are absent. Clear context without alternatives merits a 4.

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