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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered without the description. The description's remaining content is a list of returned fields, which overlaps the existing output schema rather than adding behavioral context like auth needs, error behavior, or rate limits.

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?

A single sentence, front-loaded with the usage trigger and then the returned attributes. Every clause carries information and there is no filler.

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?

With one required parameter fully documented, annotations covering the safety profile, and an output schema that handles return values, the description covers what an agent needs to select and call the tool. The only minor gap is that the returned-field list duplicates the output schema instead of spending that space on disambiguation from siblings.

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 the single plan_id parameter is documented with an example value and a pointer to search_plans for ids. The description adds no format or constraint detail beyond the schema, so the 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 names a concrete verb ('get details') and a precisely scoped resource ('one specific esimgomobile plan by id'), and enumerates the attributes returned. The singular 'one specific plan by id' implicitly separates it from the plural browse tools (list_available_plans, search_plans), though it never names a sibling explicitly.

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 leading clause 'Use when the user asks about one specific esimgomobile plan by id' is an explicit trigger condition, and the 'by id' qualifier implies it is not for browsing or comparison. There is no explicit when-not clause or named alternative, so it falls 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.