Check eSIM login status

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

Annotations already declare readOnly, idempotent, and non-destructive. The description adds valuable behavioral context: the call is local, fast, makes no network request to the eSIM platform, and the output can indicate a pending login that requires a six-digit code. This goes beyond annotations without contradicting them.

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?

Three sentences, with the purpose in the first sentence, usage timing in the second, and actionable result handling in the third. Every sentence earns its place with no 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?

Given zero parameters and an output schema present, the description fully covers what the tool does, when to use it, and how to interpret and act on the result. It is complete for an agent to select and invoke 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?

The tool has zero parameters and the input schema is an empty object, making parameter explanations unnecessary. The baseline for 0 params is 4 and the description correctly focuses on behavior rather than inputs.

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 uses a specific verb 'Check' with a clear resource 'eSIM login status' and further clarifies it checks whether the client has a signed-in eSIM user. It distinguishes itself from sibling login tools by noting it is local, fast, and does not call the eSIM platform.

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?

Provides explicit WHEN guidance: use before anything needing a signed-in user and whenever the user asks about login state. It also gives conditional actions based on the result (carry on if authenticated, ask for six-digit code if pending). However, it does not explicitly name alternative tools or state when not to use it, so it misses the top tier.

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