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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=false), so the bar is lower, and the description still adds real value: it discloses that a token unlocks extra fields, that times are reported in BRT, and critically that third-party text arrives inside 'untrusted_content' with a '_notice' and is data rather than instructions. That prompt-injection warning is exactly the kind of context annotations cannot carry.

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 sentences, front-loaded with the resource identity, then the conditional behavior, then the untrusted-content warning. Slightly telegraphic in places but no sentence is filler.

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?

With no output schema, the description does the work of explaining return shape: the untrusted_content wrapper with its _notice, plus the optional status/badge fields. An agent knows what it will get and how to treat it. Only the anonymous (no-token) response shape 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 description coverage is 100% and the token parameter's description already carries the security rationale (prefer the Authorization header because clients log arguments). The description nonetheless adds the consequential meaning of the parameter — that supplying it changes the response to include signing status and badge — which the schema alone does not state.

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 and named resource ('Read the Agents' Charter / Carta dos Agentes') and clarifies that with a token it also returns your signing status and badge, which separates it from carta_sign and carta_reserve by content rather than by name. The sibling alternatives are not explicitly named, which is the only thing keeping it from a 5.

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 conditional 'With a token, also your signing status (what is missing, exact time in BRT)' implies when to pass a token versus read anonymously, which is useful implied guidance. However, it never says when to call this instead of carta_reserve or carta_sign, nor any prerequisite for obtaining a token. Adequate but with a clear gap.

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