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

The description goes beyond the annotations by detailing the error handling (returning `_erro_upstream` instead of raising an exception on 404) and mentioning the 24-hour cache. This provides important behavioral context that is not evident from the annotations alone.

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 concise and well-structured, with clear sections for the endpoint, usage, coverage, and error handling. It avoids unnecessary verbosity while covering essential details, though a slight reduction in redundancy could make it even tighter.

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?

Given the simple parameter set and presence of an output schema, the description is complete. It explains the purpose, usage, coverage, caching, and error behavior, covering all aspects an agent would need to invoke the tool correctly.

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?

The schema already describes the single parameter, and the description adds value by specifying the exact format (14 digits, with or without punctuation) and providing a concrete example. This enhances understanding beyond the basic schema.

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 the tool's function: listing administrative units of an agency in PNCP. It includes the specific endpoint and explains its utility for discovering unit codes before filtering contracts, which distinguishes it from sibling tools that focus on other aspects.

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 indicates when to use the tool ('Útil para descobrir códigos de unidade antes de filtrar contratações/contratos') and explains the 404 behavior, referencing a pattern shared with other tools. However, it does not explicitly contrast with alternative tools, though the context is fairly clear.

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