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

Goes well beyond the annotations by disclosing that the record only appears after 'the next daily scan' (asynchronous, not immediate), the 25-endpoints-per-host cap, and the 10-calls-per-hour rate limit. It also explains the payoff — buyers' agents see the record before paying — which the idempotent/destructive hints do not convey.

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-loads the free/self-serve framing and packs prerequisites, timing, and limits into three sentences. The seven-registry enumeration is a bit listy and could be trimmed, but each sentence otherwise carries operational information.

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?

An output schema exists, so return values need not be described; the description covers what remains — cost, eligibility, verification, async timing, and quotas. Nothing an agent needs to decide whether to call this tool or to set expectations 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 coverage is 100% and the single `url` parameter is already documented with an example, so the schema carries most of the load. The description still adds a meaningful constraint: the URL must be a live x402/MPP/L402 endpoint that returns a 402 payment challenge, which is a validation requirement not present in the schema.

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?

Opens with a specific verb and resource: adding your own paid endpoint to the x402 Trust Index. It clearly separates itself from the read-only sibling x402_trust_record and from registry-listing tools by framing this as self-registration when nothing else lists the endpoint.

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?

States the exact condition for use ('when no registry lists it yet') and enumerates the registries it complements, which tells an agent when another path already covers the endpoint. It also gives a prerequisite (the endpoint must answer 402 with a payment challenge) so the agent can pre-validate before calling.

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