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

Annotations only declare the generic safety profile; the description goes far beyond it with the two-call sign-then-submit protocol, ten-minute issued_at validity, a 5-write-per-hour limit that exempts the first call, free/no-points economics, public-from-creation and Self-Reported status, one-wallet-one-passport constraint, and named refusal codes including ip_quota. It also states what the signature does and does not prove, which is materially useful for an agent deciding whether to proceed.

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?

Despite its length, it is front-loaded with the trigger, then the exclusions, then the protocol, then limits and returns, each under a capitalised header. Dense rather than padded, though the WHAT SIGNING PROVES paragraph is slightly editorial for a tool definition.

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?

There is no output schema, so the description carries the return burden and does so precisely, giving both the first-call shape ({ok, step, messages, issued_at, valid_until, next}) and the join shape (passport_id, slug, lookup_url, claim, note?). It also covers the edge case where an older passport merely lists a wallet, which an agent would otherwise mishandle.

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 already 100%, so the baseline is 3; the description earns extra by explaining the cross-call semantics the schema cannot: that the first call takes no signatures and returns the exact messages plus issued_at to echo back, and that claim_sha256 lets an owner link the passport later without the code reaching the server. It stops short of detailing the response_format parameter, but that is minor.

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 (join) and resource (Sato Hub passport) plus the mechanism (signing with the agent's own wallets, free, one step). It explicitly distinguishes itself from three sibling tools by name, so an agent can route without opening any schema.

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 'USE WHEN' / 'NOT FOR' structure names each alternative and the exact condition that selects it: onchain_agent_passport_action for changing an existing passport, onchain_agent_register_agent for the older form-style registration, onchain_agent_get_agent_passport for reading. Exclusions are as explicit as the inclusions.

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