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

Annotations already declare readOnly, idempotent, non-destructive and open-world behavior, so the safety profile is covered. The description still adds meaningful operational context that annotations cannot convey: the source is free and requires no API key, which lowers the barrier to invocation.

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?

Two sentences, front-loaded with what the tool queries, followed by the mode explanation and a usage note. Efficient and free of filler, though the opening clause and the closing usage sentence partially overlap in intent.

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?

An output schema exists, so return-shape explanation is unnecessary, and all three optional parameters are documented in the schema. The description covers both invocation modes and the no-key access model, leaving only minor gaps like pagination or result-volume expectations.

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% and each parameter (limit, query, indicator) already carries its own explanation and format hints. The description restates the indicator-code retrieval behavior but adds no syntax 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 and resource (query the WHO Global Health Observatory) and explains the two operating modes: list/filter indicators, or pass an indicator code to retrieve data values. This cleanly distinguishes it from statistics siblings such as world_bank_indicator and un_sdg.

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 clear context with 'Use for official global health statistics', and the dual-mode sentence tells the agent which mode to pick based on whether an indicator code is known. It names no explicit alternative or exclusion (e.g., when to prefer world_bank_indicator), 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.