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

Beyond the readOnlyHint/openWorldHint annotations it discloses non-obvious behavior: the `basis` field distinguishes recorded history from fallback last-build trend, and the measurement method (current score vs. first scored snapshot on or after `since`) is spelled out. It also exposes the full billing model — per-request, per-record, cap, plan inclusion, and an estimate endpoint — which is exactly the kind of cost behavior an agent needs before invoking.

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?

It is front-loaded with the tool's name and purpose before the mechanics, and the dense single paragraph has no filler. The pricing clause is long — per-request rate, per-record rate, cap, plan tiers, estimate link — and could be trimmed, but it is decision-relevant rather than redundant.

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-shape burden and does so by naming the `was`, `compared_to`, and `basis` fields. Paging behavior and edge cases for out-of-range dates are left implicit, and the `limit` param documentation in the schema covers most of the pagination gap.

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 the baseline is 3, but the description adds real meaning for `since` by defining the comparison anchor ('first scored snapshot on or after since') rather than just the date format. `limit` and `context` are left to the schema, which is acceptable since both are self-documenting.

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 states a precise verb and resource — catalog changes since a date — and enumerates the two components (providers added/updated, plus rating movement). It goes further than a generic 'what changed' by pinning the movement to a specific comparison point, which is enough to tell it apart from a plain rating-movers feed.

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 by the 'since a date' framing and the priced-operation note, so an agent can infer when this tool is relevant. However, it never names a sibling such as find_rating_movers or get_rating_history, nor states when this tool is the wrong choice, so the routing burden stays with the caller.

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