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

Annotations already supply read-only/idempotent/non-destructive signals; the description adds useful context beyond them: source (ECB SDW), no-auth requirement, and business-day frequency. No contradictions with 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?

Three sentences, each carrying distinct information: what the tool returns, how to filter, and source/auth. No filler or redundant material.

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 full schema coverage, an output schema, and annotations defining the safety profile, the description adds the missing provenance, auth, and benchmark-use context. Nothing an agent needs to call it correctly is omitted.

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. The description's filter sentence restates schema information ('Filter by tenor_years, and either last_n_observations or start_period/end_period') without adding meaning beyond the schema's own parameter documentation.

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 ('Get'), exact resource ('AAA-rated government bond spot yield curve rate'), and restricted maturity values. The 'risk-free benchmark' phrase distinguishes it from sibling ECB macro tools like hicp_inflation or key_rates.

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?

Provides clear selection context ('business-day series used as a euro area risk-free benchmark') and explicitly describes the filter combination (tenor_years plus either last_n_observations or a date range). It does not name sibling alternatives or state when not to use it, so it stops short of a 5.

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