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

Annotations already cover read-only, closed-world and non-destructive, and the description adds genuinely non-structured context: reads only the submitted material, 0.10 USDC per call on Base via x402 exact, 10 signed-wallet free calls per rolling 30 days, and X-Wever-Wallet-Proof bound to the exact arguments and route. The closing claim that the report 'matches words, figures, dates and named items... does not interpret meaning beyond that matching' is lifted from an evidence-check framing and sits awkwardly beside the structural field-diff promise, slightly muddying what the tool actually does.

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 purpose is front-loaded, which is good, but the block is dense: four separate negations ('no page fetch, no account access, no merchant contact and no money movement'), payment mechanics, contract path and a human URL all crowd one paragraph. The trailing matching-limitation sentence adds length without adding clarity about the diff output.

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 no output schema, the description does carry the return burden: a signed report listing added, removed, type-changed and format-changed fields by JSON pointer, plus an Ed25519 signed receipt. Payment model, auth binding and processing boundaries are all present. The only shortfall is the ambiguous final sentence, which leaves the exact report contents partially unresolved.

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 100%, so the schema already documents all five parameters including the 256 KB string limit and the endpoint pattern. The description contributes only the relationship semantics of before/after being the same response in two versions, and says nothing about endpoint, before_label or after_label beyond what the schema states. 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 concrete verb and resource: submit two samples of the same API response (before/after) and get back a signed report of fields added, removed, type-changed and format-changed, addressed by record-relative JSON pointer. The comparison scope is more specific than neighbours such as wever_changelog-check or wever_contract-diff-check, and the sibling lineage (wever_data-evidence-check field analysis) is named.

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 triggering scenario is unambiguous — you must already hold two versions of the same response, supplied as JSON or its serialized string. It does not explicitly say when to prefer this over similar diff-style siblings (wever_changelog-check, wever_contract-diff-check, wever_data-evidence-check), so the agent must infer routing from the input shape rather than from stated exclusions.

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