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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely useful context beyond that: it is 'Free, no model call', and the signing keys come from SNHP's published /.well-known/ucp endpoint. It does not discuss failure modes beyond the names of the problem categories.

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?

Two dense sentences, front-loaded with the verification scope, then cost and return shape. Listings of return fields ('{ok, problems, checks, signed_by_snhp, signatures}') is slightly redundant given an output schema exists, but the text is tight and earns most of 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?

With an output schema, annotations, and fully documented parameters, the description carries little remaining burden and is essentially complete. Repeating the return object is harmless but unnecessary; nothing an agent needs to invoke it is missing.

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% and the description largely mirrors it ('the seller's own policy', 'the receipt returned with a deal'). It adds no syntax, format, or shape detail beyond what the schema already provides, so the baseline 3 is appropriate.

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 precise verb ('Verify') and resource ('signed deal receipt') and enumerates exactly what is checked: both signatures, key ownership against /.well-known/ucp, policy digest, and rule re-checks. An agent can tell this apart from check_offer_policy/compile_offer_policy at a glance.

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?

Usage is implied by the domain ('the receipt returned with a deal', 'the policy the deal was made under'), but there is no explicit when-to-use, when-not-to-use, or named alternative among the siblings (check_offer_policy, compile_offer_policy). Adequate but leaves routing to inference.

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