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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds real value: it explicitly states the tool does not perform the install (the actual mutation happens off-platform) and discloses the auth requirement ('Needs the user's Cotlet API key with access to this app'). It stops short of stating failure modes or rate limits, but adds useful context 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 key content is front-loaded, but the same artifacts (QR code, SM-DP+ address, activation code) are stated twice in the first two sentences, and the 'Install or share, Share and more' phrasing is repeated. It earns its place overall but carries noticeable redundancy.

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?

There is no output schema, so the description carries the burden of describing returns, which it does concretely (QR image plus manual codes, including a conditional confirmation code). Combined with annotations and a fully documented single parameter, the agent has what it needs to call this correctly.

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 esim_id parameter is documented ('eSIM ID from list_esims'). The description adds no additional meaning about the parameter, so the baseline of 3 applies.

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 (get install instructions for an eSIM) and enumerates the exact artifacts returned: a QR code image, SM-DP+ address, activation code, and optional confirmation code. This is specific enough to distinguish it from airalo_get_esim or airalo_buy_esim without opening a schema.

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?

Usage is only implied: the clarification that 'The tool does not install anything; you scan the QR code or enter the codes on the phone' signals it is a post-purchase informational step, but no alternative is named and no explicit when-to-use condition is given. Adequate but leaves the agent to infer the workflow position.

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