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

Although read-only and idempotent are already in annotations, the description adds valuable behavioral detail: up to 10 results, relevance ordering, empty list meaning no match, and the fact that the catalog comes from a public source and is cached in memory. This goes well beyond the 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?

The description is front-loaded with the core behavior and return format, then efficiently covers contract context, alternatives, query expectations, and behavior in separate short sections. Each sentence adds practical value.

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?

For a single-parameter catalog search tool, the description is complete: it defines the result contract, ordering, empty-result behavior, language support, and how to continue the workflow via `fetch`. Nothing invocation-critical is missing.

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?

The schema already fully documents the `query` parameter, so the baseline is 3. The description adds meaningful extra context by specifying supported languages ('Portuguese or English') and reiterating that natural language or keywords are acceptable.

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?

The description clearly states a specific verb ('Searches'), a specific resource ('UNESCO UIS statistics catalog'), and the exact result shape ('{ id, title, url }'). It also differentiates itself from the uis_* tools by calling itself 'a catalog index, not a data query.'

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 description explicitly tells the agent when to use this tool versus alternatives: pass returned ids to `fetch`, and prefer `uis_*` tools for direct data questions. This is highly actionable and leaves no ambiguity about tool selection.

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