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

With no annotations, the description carries the burden and does well: it discloses the non-destructive/no-creation guarantee, the authentication prerequisite ('Requires the store's own authenticated Correios contract'), and the provenance requirement for prepostagemId. Minor gaps remain around link expiry and failure modes (e.g. what error is returned if the pré-postagem exists but the PDF is not yet ready).

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-loaded with the action, then trigger conditions, then the alternative route, then the constraint. Every sentence carries either a use case, an exclusion, or a prerequisite; nothing is restated from the title or schema.

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?

Output schema exists so return values need no explanation, and parameters are fully covered by the schema. The description covers usage routing and prerequisites for a simple 2-param read tool. Only link lifetime/short-lived-ness of a 'fresh' download link is left implicit.

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%, so the baseline is 3, but the description adds real routing semantics: prepostagemId is the id returned by generate_label and must not be confused with the supportCode of a label attempt. That cross-field disambiguation is value beyond the schema text.

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: 'Get a fresh download link for the PDF of an already-created Correios pré-postagem by its id.' It also distinguishes itself from siblings by name, explicitly excluding creation ('Never creates a new pré-postagem') and pointing to recover_label_pdf and generate_label for other cases.

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 concrete when-to-use triggers ('when generate_label's link reason was label_pdf_timeout', 'to re-check status later') and an explicit alternative with its selecting condition ('if you only have the supportCode ... use recover_label_pdf instead'). The negative case is stated too: it never creates a new pré-postagem.

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