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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and closed-world scope, so safety is covered. The description goes beyond them by disclosing the transient empty-list state during provisioning and its expected duration, plus the dual-credential identification requirement, which is genuinely useful operational context.

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?

Front-loads the verb and resource, then the identification rule, then the empty-result caveat. Every sentence carries information, though the long enumeration of return fields is somewhat redundant given an output schema already exists.

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?

Covers the purpose, the exact credentials needed, the identification constraint, and the transient emptiness behavior. With an output schema handling return structure, nothing an agent needs to invoke this correctly is missing.

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 coverage is 100%, so the baseline is 3. The description adds meaning beyond the schema by explaining that the order id alone does not identify a buyer and must be paired with the purchasing email, which clarifies why both parameters are required rather than merely listing them.

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 the installable eSIM(s) for a paid order') and enumerates exactly what is returned (QR code, LPA string, SM-DP+ address, install links, hosted install page). This is clearly distinguishable from siblings like get-order-status or check-esim-usage without opening any 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?

Gives clear context for when the tool is appropriate (a paid order, identified by order id plus buyer email) and discloses a timing condition: an empty esims list while provisioning is in flight, clearing within a minute of payment. It does not explicitly name an alternative tool for the pre-payment or non-eSIM case, so it stops short of full when/when-not routing.

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