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

Annotations only declare the safe-read profile (readOnly, idempotent, non-destructive); the description adds real temporal semantics beyond that, explaining that verdict_since can span unmeasured weeks because scans lacking the resource don't break the run, and that currency derives from last_checked_at and in_latest_scan. It does not cover error behavior when the URL is unknown.

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 what the tool returns, then immediately qualifies the two timestamp fields whose naive reading would mislead. The density is justified because there is no output schema to explain these fields elsewhere; no sentence is filler.

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 one parameter, no output schema, and only read-only annotations, the description responsibly covers both the payload contents and the timestamp interpretation that an agent would otherwise get wrong. What is missing is the not-found/no-data case and any auth or scope prerequisite.

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 0% and the only property is a bare 'Url' title, so the description must carry the load. It does so by specifying that the URL must be exact and include path and query, which is meaningful input guidance. It could still state matching rules or failure on no-match.

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 resource and operation: the latest payability observation for one exact resource URL, enumerating what comes back (verdict meaning, remediation, per-network options). It is clearly distinct from siblings like host_summary or find_endpoints in tone, but it never names an alternative to route the agent explicitly.

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 rather than stated: the parenthetical '(path and query included)' signals this is a per-URL lookup, not a host- or catalogue-level one, which is the key selection constraint against host_summary/catalogue_stats. There is no explicit when-to-use or when-not-to-use statement.

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