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

With no annotations, the description carries the burden and does disclose two useful traits: the feature is early access, and the call requires no authentication. It is silent on idempotency (what happens if the email is already listed), whether a confirmation is sent, and whether the write is reversible — meaningful gaps for a mutation tool.

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 short clauses, and the operational instruction is easy to extract. The leading clause is partly product framing rather than invocation guidance, which is mild padding but not serious waste.

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?

For a simple two-parameter, no-output tool this covers the essentials: what it does, auth status, and a usage gate. Missing are the outcome of the call and duplicate-handling behavior, which the agent may need when a user has already signed up.

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 50%: the optional 'note' parameter is documented in the schema itself, while 'email' is self-explanatory by name. The description adds no meaning beyond the schema, but the remaining gap is small for a two-parameter tool.

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 concrete action (add the user's email to the early-access waitlist for continuous CNPJ monitoring) and names the resource. The verb+resource pairing is clear, though it never explicitly separates itself from close siblings like wait_for_changes or signup.

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?

"só use se ele pediu" is an explicit gating condition telling the agent not to call it unprompted, which is exactly the kind of guidance that matters for an opt-in list. It does not name an alternative tool or explain what to do if the user wants monitoring but has not asked to join the list.

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