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

Annotations declare readOnlyHint=false, openWorldHint=true, destructiveHint=false. The description adds meaningful behavioral context: it says the tool will 'create or replay' the exchange account, signaling idempotency, and that it 'activate[s] one scoped credential generation', which is a side effect. It also communicates the security-relevant proof requirement. This goes beyond the annotations in a useful way, though it does not describe failure modes or what exactly 'replay' implies.

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?

One dense sentence packs a conditional trigger, a sequence of operations, and the credential-generation outcome. It is front-loaded and free of filler. It is somewhat jargon-heavy and reads like a spec summary, but every phrase contributes meaning and the length is appropriate for the tool's complexity.

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?

Given the complexity (nested completion object, proof requirements, scope constraints) and the lack of an output schema, the description provides a useful high-level map of what the tool does and its key precondition. It lacks an explicit statement about return values or the relationship to request_participant_challenge. For a complex tool, it is nearly complete but still leaves some behavioral and workflow gaps.

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 description says 'prove Ed25519 key control' and 'activate one scoped credential generation', which loosely maps to the completion payload's proof and requestedScopes fields. However, schema description coverage is 0%, so the description does not compensate for the nested completion structure. In practice, the rich inline schema with patterns, required fields, and the proof construction note carries the semantic load, making the description supplementary rather than primary.

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 names a specific verb and resource: completing participant registration. It clarifies the internal actions (prove Ed25519 key control, create/replay register_agent exchange account, converge D1 projection, activate scoped credential generation), which makes it distinguishable from request_participant_challenge. However, it does not mention sibling tools or explicitly state that it is the final step in a multi-step registration flow, so some ambiguity remains.

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 precondition 'When lifecycle state is ACTIVE' gives a clear contextual trigger. It implies that this tool should be used only after prior registration steps and that other tools like request_participant_challenge must have been called before. But it does not explicitly state when not to use it or mention alternatives or prerequisites by name. The guidance is present but not fully explicit.

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