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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false. The description adds behavioral context beyond those: it explicitly states the tool performs a login to the official backend and returns the session token, branches, and user data. This clarifies the nature of the operation (a validation, not a persistent connection) and what the response contains, complementing the annotations without contradiction.

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 two sentences: the first explains what it does and returns, the second provides usage guidance. Every sentence carries essential information with no filler or redundancy, making it highly efficient and well-structured.

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?

Despite having no output schema or parameters, the description covers the tool's core purpose, the action performed (login to official backend), the success indicator (returns if it worked), and the specific data returned (token, branches, user data). It also gives a concrete use case. While it could mention potential failure outcomes or prerequisites, the description is adequate for a simple credential check with full annotation support.

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?

There are 0 parameters, so the baseline of 4 applies. The description does not add parameter details because none exist. It implicitly covers the tool's scope by explaining what the login validates, which aligns with the zero-parameter 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 uses a specific verb 'Valida' (validates) and resource 'credencial webPosto', clearly stating it logs in and returns whether it succeeded along with the login body (session token, branches, user data). It distinguishes itself from siblings by focusing on credential validation for confirming CNPJ/user/password correctness, making its purpose unambiguous.

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?

Explicit usage guidance is provided: 'Use pra confirmar que CNPJ/usuário/senha estão corretos e que o dispositivo foi liberado no painel' (use to confirm credentials are correct and device is released). While it doesn't explicitly list alternatives or when-not-to-use, it clearly advises when to invoke this tool, which is sufficient context for a simple validation check.

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