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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds important provenance and reliability context: 8 tables hand-transcribed from ministry documents and 67 read from the WHO database, plus source URL and review date. 'A transcribed table, not a recollection of one' further signals evidence-based output.

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 description is front-loaded with the core purpose and return contents. It is somewhat dense with provenance details, but those details are relevant and the final routing sentence is concise.

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?

Given the existing output schema and full schema description coverage, the description supplies all additional context an agent needs: country coverage, data provenance, age-based conditional output, and alternative tool routing.

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 schema already documents lang, country, and age_months with enums and ranges. The description reiterates that age_months triggers 'due now' and 'next' output, but adds no syntax or format detail beyond the schema.

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 and resource: the official childhood vaccination schedule for 75 countries. It specifies the return contents (ages, vaccines, protection, issuing body, source URL, review date) and distinguishes itself from paediatric_question_with_sources.

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?

Gives explicit when-to-use guidance: 'Use when asked which vaccines a child gets, or are due, in a given country.' It also names the alternative for a different need: 'For what a vaccine does or its side effects use paediatric_question_with_sources.'

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