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

The annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false), so the description's main added behavioral value is the 'free' note and the domain scoping to GOV.UK evidence sources. It does not describe pagination, freshness guarantees, or failure behavior, but those are less critical given the zero-parameter read-only nature and rich output schema.

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 description is two sentences, begins immediately with the core identity, lists the intended uses in a compact comma-separated form, and closes with a single clear exclusion. Every clause earns its place and there is no fluff.

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 zero-parameter, read-only, idempotent status tool with an output schema and comprehensive annotations, the description is complete. An agent knows what the tool is for, what it is not for, and has the full suite of use cases without needing extra detail.

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?

The tool has zero parameters and the schema description coverage is 100%, so there are no parameter meanings for the description to add. The rule baseline for zero-parameter tools is 4, and the description appropriately focuses on use cases rather than trying to document nonexistent parameters.

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 identifies the resource as GOV.UK evidence source status and enumerates the kinds of questions it answers (freshness, stale sources, changed fingerprints, blocking sources, review status, lifecycle, coverage). It doesn't state an explicit verb like 'returns' or 'checks', but the use-case list and the exclusion of sponsor change decisions make the purpose clear enough to distinguish it from the sibling change-assessment tools.

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?

It explicitly lists when to use the tool ('Use for current guidance, source freshness, stale sources, changed fingerprints, blocking sources, review status, evidence lifecycle, or source coverage') and provides a clear when-not-to-use case ('Not for a specific sponsor change decision'). This gives an agent direct routing guidance, even though alternative siblings are not named.

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