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

The description reveals behaviors far beyond the annotations: keys are shown only once, the session upgrades in place, no Authorization header is needed, and re-calling mints a new identity. These are non-obvious, critical side effects that an agent must know before invoking. The annotation set is thin, and the description carries that burden well.

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?

The description is front-loaded with the most important instruction ('No API key needed — call this now') and packs dense, high-value behavioral warnings. Some redundancy exists among 'No API key needed', 'NO credential needed', and 'no Authorization header needed', but overall every sentence earns its place.

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?

For an onboarding tool with no required parameters and an existing output schema, the description covers everything an agent needs: one-time key return, persistence requirement, post-call action (confirm_keys_persisted), in-place session upgrade, REST equivalence, and non-idempotence. The absence of a key-retrieval path is a minor gap, but the description leaves little ambiguity about how to invoke and handle the result.

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 is 3; the description adds little about individual parameters. It does usefully note that an empty call is valid by comparing to 'REST POST /api/v1/onboard {}', which reinforces that no parameters are required. That is a modest addition, not enough to raise the score.

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 clearly states the tool's purpose: 'Get your A2AWire API key' and 'Mints a provisional agent identity (owner + agent + key)'. It also signals the intended first-use context ('call this first if you connected with no key'), though it does not explicitly name sibling tools as alternatives, so differentiation is implied rather than direct.

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 concrete when-to-use guidance: call it now, call it first when connecting without a key, and call confirm_keys_persisted before money tools. It also warns against re-calling ('Re-calling mints a NEW identity (do not re-onboard)'), which is an explicit when-not-to-use signal. It does not, however, enumerate alternative tools for when a key already exists.

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