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

Annotations already establish readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds valuable provenance context beyond that: 'Original bank data free' and 'Not independently verified' are data-quality caveats an agent cannot get from annotations, plus temporal coverage and change-frequency characteristics.

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 every clause carries provider-specific facts. The semicolon-chained run-on is dense and slightly harder to scan than a bulleted form, but there is little wasted text.

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 an output schema present, return values need not be explained, and the description still covers coverage, units, freshness, source notes and a verification disclaimer. It is complete for a single-enum directory tool, with only the sibling-routing guidance being thin.

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% and the enum is already documented, so baseline is 3. The description goes further by mapping each provider value to concrete content and time spans (fed's pre-1994 target reconstruction, ecb's sparse dates of changes), adding real meaning beyond the enum names.

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 ('Discover') and resource ('official policy rates' as a series directory), and enumerates exactly what each provider returns (boe UK Bank Rate since 1975, fed eight US series, ecb three instruments, boc two Canadian series). This clearly separates it from data-fetching siblings like get_interest_rates. It stops short of explicitly naming that sibling, so differentiation is implied rather than stated.

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?

'Inspect coverage, units, freshness and source notes' hints at the discovery-first workflow, and the schema notes the returned directory supplies compatible series identifiers. However, there is no explicit 'call this before get_interest_rates' instruction or when-not-to-use guidance, so the agent must infer the catalog role.

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