Read plan limits, usage and balances

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

Annotations already declare readOnlyHint, destructiveHint=false, and idempotent, but the description adds valuable context: it states 'Read only. Nothing is changed' (reinforcing but slightly redundant) and reveals an authentication requirement: 'Needs a secret key (wv_sk_) carrying the meta:read scope.' It also hints at response semantics by explaining the balance will 'move' after a run. This exceeds the annotation baseline.

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 efficiently structured: purpose (first sentence), clarification (second), usage guidance (third), safety note and auth (final sentences). Every sentence carries meaningful information, and the overall length is appropriate for the tool's simplicity. No filler or repetition beyond the minor 'Read only' / 'Nothing is changed' 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?

The description fully covers the tool's purpose, usage timing, safety (read-only), and auth scope. Since there is no output schema, the description compensates by summarizing what the response contains ('what your plan allows... what you can still spend'). For a parameterless read-only tool, this is complete and actionable context.

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 schema shows no properties, so schema coverage is trivially 100%. With no parameters to document, the description cannot add parameter-level detail, but it does convey the data scope (plan limits, usage, balances) which is what the tool returns. The baseline for 0 params is 4, and the description meets 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?

The description opens with a specific verb and resource: 'Read plan limits, usage and balances.' It further clarifies the meaning with 'What your plan allows, what you have used in the current period, and what you can still spend,' which clearly differentiates it from sibling tools like get_site_info or list_articles. The purpose is explicit and unambiguous.

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 provides explicit usage context: 'Read this before a pipeline run if you want to fail fast rather than handle a 402, and read it after a run to see the balance move.' This tells the agent when to invoke the tool and why, offering clear scenario-based guidance. Although no alternative tool is named, the unique purpose makes the usage direction highly actionable.

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