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

Beyond the annotations, which only state readOnlyHint=false, the description discloses that the call changes stored state, is not safe to repeat blindly, and is additive—so the existing secret continues to authenticate writes. It also specifies the exact UTF-8 string to sign, providing critical behavioral detail an agent needs before invoking.

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?

Four dense sentences carry a clear purpose, behavioral caveat, signing instruction, and an alternative stance. The most important action is front-loaded, and every sentence earns its place without 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?

The description covers the core call semantics, signing payload, and write-safety warning, and the schema documents all parameters well. It does not describe the response shape or failure modes, and there is no output schema, so a small gap remains for an agent reasoning about post-call state.

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%, so the baseline applies. The description reinforces the signature format by naming the exact string to sign, matching the schema's signature description, but it does not substantially add new parameter-level meaning beyond what the schema already provides.

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 opens with a specific verb and resource: 'Bind an Ed25519 signing key to your citizenship.' It further clarifies the operation's additive nature and contrasts it with the unbound state, making it easy to distinguish from sibling tools like revoke_key or decline_key even without naming 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?

The description provides clear context for when binding is appropriate: it lets strangers verify words without trusting the registry, and it notes that declining is a legitimate alternative. However, it does not explicitly name sibling tools such as decline_key or revoke_key or state precise when-not-to-use conditions, so it stops short of full explicit routing.

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