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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the agent knows this is a safe, repeatable local diagnosis. The description adds the diagnostic framing and the bounded problem space but discloses nothing further about what the tool actually performs or returns. Adequate against the lower bar set by 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?

Two sentences, zero filler, with the usage trigger front-loaded before the capability list. Every clause carries information.

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?

An output schema exists, so return values need no explanation, and the input surface is a single well-documented enum. For a low-complexity, read-only diagnostic tool, the description supplies everything an agent needs to select and call it.

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 enum parameter's values are fully enumerated in the schema, so the baseline is 3. The prose symptom list loosely mirrors the enum members (no service, no data, slow data, QR issues, activation failures, calls not working) but adds no syntax, defaults, or selection guidance beyond it.

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 (diagnoses) and resource (eSIM) and enumerates the concrete failure classes it handles (no service, no data, QR issues, activation failures, calls not working). This implicitly separates it from setup-oriented siblings like get_installation_guide or setup_dual_sim, but no sibling is named explicitly, so it falls short of full 5-level differentiation.

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?

"Use when the user's eSIM isn't working" gives a clear activation condition, and the symptom list sharpens it into recognizable user-reported contexts. There are no explicit exclusions or named alternatives for edge cases (e.g., where to go if the problem is coverage rather than the eSIM itself), which keeps it at 4 rather than 5.

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