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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds value the annotations cannot: it is the only source for what is returned (address, plan, allowance) since there is no output schema, plus a recommended call order. No auth or rate-limit detail is given.

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 short sentences, no filler, with the actionable ordering cue ('Use this first') front-loaded before the payload and the follow-up use case. Every sentence carries distinct 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?

For a zero-parameter, read-only tool with full annotation coverage and no output schema, the description supplies both the return contents and the usage trigger. It is essentially complete, with only marginal omissions such as what the plan values look like or how many addresses may appear.

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 takes zero parameters, so the baseline is 4; there is no parameter surface for the description to clarify or obscure.

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 and enumerates the returned payload ('@agentline.nz email address(es), plan and remaining email allowance'), which is far more specific than the title alone. It does not, however, explicitly differentiate itself from plausible siblings such as get_profile or get_my_number, so sibling differentiation is left to inference.

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 this first' gives explicit ordering guidance, and the second sentence names a concrete use case (services that verify the agent by email). It stops short of naming an alternative tool or stating when-not-to-use, which a 5 would require.

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