List eSIM destinations

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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds valuable behavioral context beyond annotations: the result is 'deliberately a limited extract plus a total count', and 'This needs no login' clarifies access requirements. This goes well beyond what the annotations provide.

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 short and front-loaded with the core purpose. The 'WHEN' label organizes usage guidance clearly. Every sentence earns its place with no fluff or repetition.

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 simple list tool with an output schema, the description adequately covers purpose, usage, and result behavior. It explains the limited extract nature and instructs the agent to ask the user where they are travelling, which is critical for effective interaction. No gaps remain.

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%, with detailed parameter descriptions for limit, query, and locale. The description complements the schema by clarifying query usage ('Pass the user's own wording as 'query' to resolve it') and browsing behavior ('omit 'query' to browse'), adding value 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?

The description clearly states the tool's purpose: 'List the countries the eSIM platform sells plans for, or check the one the user named.' This uses a specific verb and resource and distinguishes it from siblings like list_regions and find_bundles_by_country.

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?

Explicit WHEN guidance is given: 'WHEN: the user asks which destinations are available, or you want to confirm a country exists before searching for plans.' It also explains how to use the query parameter ('Pass the user's own wording as 'query' to resolve it; omit 'query' to browse') and what not to do ('do not read the whole list out').

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