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

Annotations only declare readOnlyHint=false, so the description carries the burden of explaining the write behavior. It does this well with 'WRITES: this call changes stored state and is not safe to repeat blindly,' which discloses non-idempotency beyond the annotation. It also adds the rotation requirement context. No contradiction with annotations.

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 with the purpose front-loaded, a clarifying caveat, and an explicit write warning. Every sentence adds decision-relevant information and there is no filler or repetition of schema details.

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?

The description covers the core purpose, the write side effect, and the rotation condition. However, the secret parameter is undocumented in both schema and description, and the 'rotation statement' is referenced but not specified. For a write operation with no output schema, an agent still lacks some details for fully confident invocation.

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 high at 83%, so the baseline is 3. The description adds meaningful conditional semantics by stating that rotation makes old_sig and new_sig required, which is not clear from the schema alone. However, it does not explain the undocumented secret parameter.

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 verb-resource pair: 'Register or rotate a witness pointer where your countersignatures live.' It further clarifies the scope by noting that a pointer is not an endorsement and by distinguishing rotation via old_sig/new_sig, so an agent can tell this tool apart from generic siblings like register or rotate.

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 gives clear context for when to call this tool: to register or rotate a witness pointer. It also provides a concrete prerequisite for the rotation path ('requires old_sig and new_sig over the rotation statement'). It does not explicitly name alternatives or exclusions, so it stops short of a 5.

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