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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety and locality are covered. The description adds genuinely new operational context — no API key required and no charge — which an agent cannot derive from the annotations, plus a hint that API limits are disclosed in the response.

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?

Two short sentences, front-loaded with what the tool covers and followed by the practical constraints (no key, no cost). No filler, no repetition of the title, and every clause carries information.

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?

An output schema exists, so return values need not be spelled out; the description only needs to say what the response covers, which it does (products, UFs, per-tool outputs, limits). For a zero-parameter informational tool this is complete.

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 tool takes zero parameters and the schema confirms an empty object, so there is no parameter semantics to explain; the baseline for a parameterless tool applies. Nothing in the description misleads about inputs.

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 states a specific resource and scope: a summary of what FiscalAPI queries per product and UF, what each tool returns, and the API's limits. That is clearly a meta/coverage tool, distinguishable in kind from the consultar_* and baixar_* siblings, though it never names or explicitly contrasts them.

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?

Usage is only implied: an agent can infer this is a discovery/informational call to make before or instead of the consulting tools. There is no explicit 'use this when...' or 'do not use this to fetch actual data' guidance, and no mention of when the sibling tools should be preferred.

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