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

readOnlyHint=true already covers the safety profile, but the description adds real value by disclosing the API method (GET /statistics) and, crucially, the shape of the returned data (summary metrics plus optional charts) that no output schema provides. It does not mention rate limits or auth, so it stops short of a 5.

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-loaded with the core purpose and scope, then the metric/chart inventory, ending with the endpoint. Dense but every clause carries information; only the lengthy chart enumeration makes it slightly list-heavy.

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 readOnlyHint and full schema coverage, the main gap is the return payload, which the description addresses by naming the metrics and chart categories. Missing only output structure and any aggregation/pagination behavior, so it is nearly complete for a read-only statistics 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 description coverage is 100%, so every parameter (dates, hourly, region_id, pull_zone_id, load_* flags) is already documented in the schema. The description restates chart and scope concepts but adds no format or default detail beyond the schema, so the baseline 3 applies.

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 verb+resource (get CDN statistics) and enumerates the returned metrics (bandwidth, origin traffic, requests, cache hit rate, response time) and scope (account or a single pull zone). The 'CDN' framing implicitly separates it from bunny_get_storage_zone_statistics, so an agent can place it without opening a schema.

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?

The 'account or one pull zone' phrasing implies the scoping decision, but there is no explicit when-to-use guidance, no exclusions, and no named alternative (e.g. bunny_get_storage_zone_statistics for storage zones, which is a genuine sibling). Usage is inferable rather than stated.

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