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

Annotations only declare readOnlyHint=true; the description goes further by disclosing the temporal limitation ('snapshots start when monitoring begins') and an auth requirement ('Requires key'). It does not cover return volume, pagination, or rate limits, but the added context is substantive.

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?

Three tight sentences with the core action front-loaded, followed by eligibility and auth constraints. No filler, though the final 'Requires key' fragment is terse enough to be slightly ambiguous.

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?

For a read-only tool with a rich 100%-documented schema and annotations covering safety, the description supplies the missing operational context (eligibility, snapshot start, auth). No output schema exists, but the description names what is returned, so little is left unclear.

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%, so both parameters are already documented, and the baseline is 3. The description adds only marginal meaning: it scopes url to a single page and hints that a key is required, without clarifying the header-vs-parameter choice the schema raises.

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?

The description gives a specific verb (read) and resource (fingerprints and timestamps from monitored versions of a GOV.UK page), so the agent knows exactly what comes back. It differentiates implicitly from siblings like page_changes and inspect_govuk_page by scoping to 'monitored versions', but never names an alternative 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?

'Available only for fixed pages or your registered watches' states an eligibility precondition, which is useful, but the description never says when to pick this tool over page_changes or inspect_govuk_page. Usage is implied rather than routed.

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