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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), but the description adds genuinely new behavior: hash mismatch forces verdict='deny', and quota limits (5 free calls/IP, 402 top-up on exceed). It stops short of describing output shape or latency, but output schema exists, so the remaining gap is small.

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?

Front-loaded with the primary action and mechanism, then conditional behavior, then sibling routing. Dense but nearly every clause carries information; the inline example URL is arguably redundant with the schema examples.

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 annotations, a full two-parameter schema, and an output schema all present, the description supplies everything missing: gating semantics, payment/quota behavior, and tool routing. An agent can call this correctly without further inference.

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 baseline is 3; the description adds meaning by explaining the consequence of each mode — passing a digest enforces zero-drift gating, omitting it reads/auto-pins the live digest. This is more than a restatement of the schema text.

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 ('gate'), a precise resource class (remote MCP, A2A, or x402 endpoint), and the three concrete mechanisms (JSON-RPC reachability probe, SHA-256 tools/list hashing, injection scanning). It is clearly distinguishable from siblings, which are named in the same breath.

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?

Explicitly says when to use it ('before tool execution or payment') and routes to each alternative by condition: assay_probe for registration/telemetry, assay_get_ledger_policy for stored policy hashes, assay_verify_delivery after payment. Both when-to-use and when-to-use-something-else are covered.

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