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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds substantial context on top: the coverage boundary ('Coverage starts 2026-08-31'), the shape of each returned entry (from → to, effectiveFrom, official source, verifiedDate, maintainer note), and that output is a versioned verified-changes/0.1 protocol document. These are exactly the constraints an agent needs and cannot get from annotations.

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 core purpose is front-loaded correctly, but the body is a single ~250-word run-on sentence that re-lists all twelve enum values and then dumps an exhaustive catalogue of every domain, dataset and jurisdiction covered. Much of that enumeration duplicates the schema enum and belongs in docs, not the tool description.

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 no output schema, the description carries the return-value burden and does so — entry field breakdown, protocol identifier, spec URL, and the human-facing changelog/feed URLs. Combined with the disclosed coverage start date, an agent has everything needed to call and interpret this tool.

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%, which sets a baseline of 3, and the description usefully reinforces the semantic intent of `since` as 'your training-cutoff date' rather than an arbitrary interval. The area list is repeated verbatim from the enum and adds no new meaning, but the `since` guidance lifts it above baseline.

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 opening clause states a specific verb and resource — 'what has changed in Data Butler's verified datasets since a date' — and immediately scopes it to post-cutoff knowledge. It also names the concrete data domains, which distinguishes it cleanly from point-lookup siblings like uk_rates_lookup and take_home_pay.

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 gives a clear triggering condition — 'pass your training-cutoff date to learn which ... thresholds ... changed after your knowledge ends' — which tells the agent exactly when this tool applies. It does not, however, name sibling alternatives or state when NOT to use it (e.g., use uk_rates_lookup for a single current value), so routing is implied rather than explicit.

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