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

Annotations already indicate the tool is not read-only and not idempotent. The description adds the two-step confirmation behavior (confirm: true to send) and the 500-character limit, which are not captured by annotations. It does not contradict annotations and provides useful behavioral context beyond the structured fields.

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 description is two short sentences with no redundant words. It front-loads the primary action and then adds the critical two-step detail. Every sentence 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?

For a simple send operation, the description is mostly complete but lacks any information about the response format or error conditions (no output schema). The two-step nature is only partially explained; the schema provides the 'preview' detail, but the description does not. Given the simplicity, it is adequate but has gaps.

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 67%: iccid and confirm have descriptions, while message only has maxLength. The description repeats the 500-character limit (already in schema) and mentions confirm: true to send (also in schema). It adds no new semantic meaning beyond the schema, so a baseline score of 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 clearly states the action: sending a text to the device holding an eSIM. It specifies the resource (eSIM) and the verb (send), and distinguishes from all sibling tools (e.g., topup_esim, suspend_esim) which perform different operations. The max length detail adds precision.

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 description implies when to use the tool (to send an SMS to an eSIM) but provides no explicit guidance on when not to use it or which alternative to choose. There is no mention of prerequisites like an active eSIM or contrast with other messaging tools. The usage is clear from context but not explicitly stated.

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