list_plans

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

With no annotations, the description carries the burden. It discloses the 'cheapest first' ordering and the single-country limitation, which are behavioral details not in the schema. However, it does not mention result size limits (the 'limit' param) or potential error behavior, so it is not fully transparent.

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 compact sentences with no filler. The first sentence states the primary action and ordering; the second gives a conditional alternative. Every word earns its place.

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?

The description is sufficient for a simple list tool: it specifies the single-country scope, ordering, and a sibling alternative. While there is no output schema and no mention of pagination or return format, the limited complexity of the operation and full schema parameter coverage make this adequately complete.

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 explains all parameters (country, days, limit, min_data_gb). The description adds no extra parameter meaning beyond the single-country scope already reflected in the schema, thus baseline 3 is appropriate.

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 uses a specific verb ('List') and resource ('eSIM plans'), scopes to 'one country', and adds ordering ('cheapest first'). It also distinguishes from the sibling tool plan_trip for multi-country trips, making it unambiguous.

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?

Explicitly states when NOT to use: 'Use plan_trip instead when the user is visiting more than one country.' This provides a clear exclusion and names the alternative tool, giving strong usage guidance.

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