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

Annotations already declare readOnly, idempotent, non-destructive and non-open-world behavior, so the safety profile is covered. The description adds that the result is a 'document' in 'ChatGPT deep research format', which is useful framing, but with an output schema present this is largely redundant rather than new behavioral disclosure.

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 short sentences, front-loaded with the core action, with no wasted filler. The parenthetical gloss and format note add slight length but are defensible.

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?

Output schema and rich annotations mean the description need not explain returns or safety. For a one-param read tool this is nearly sufficient; the only gap is not clarifying which search path supplies the id.

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?

One parameter with 0% schema description coverage, so the description must carry the load. It does add the key semantic that the id comes from prior search results, but it never specifies id format or provenance for the non-search_esims path, leaving the single required param only partially explained.

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: fetch one esimoa eSIM plan by id, returned as a document. It also explicitly distinguishes itself from get_esim for search_esims results. Minor ambiguity remains because 'search' is not disambiguated from the sibling search_esims.

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 an explicit routing rule: plans found with search_esims should use get_esim instead, which implies this tool serves results from the other ('deep research') search path. No explicit exclusion for when fetch is wrong outside that implied split, so it stops short of a full when/when-not statement.

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