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

Annotations already cover read-only, idempotent, non-destructive behaviorhol, so the description adds value by specifying that `used`/`remaining` are null on unmetered plans and that hard-capped plans return HTTP 402 quota_exceeded on sends. This is useful behavioral context beyond the annotations, though it doesn't detail the full response structure beyond those 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 sentences and front-loads the core purpose before adding edge-case details about unmetered plans and quota failures. Every sentence adds value, though the technical HTTP 402 detail could be slightly trimmed without losing essential meaning.

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 the tool's simplicity (no params, no output schema), the description covers the key behavioral nuances: null values on unmetered plans and quota enforcement. It's complete enough for an agent to know when to call it and what to expect, though it could mention that this is account-scoped rather than template/webhook-scoped.

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?

There are zero parameters)Skip the schema covers 100% of parameter docs by having none, so the description carries no parameter burden. The tool's no-argument nature is implicit but the description adds clarity by explaining the output fields' semantics (used/remaining null on unmetered plans). This is enough given no params exist.

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 tool returns the workspace's plan, subscription status, and month-to-date usage against quota, and it also names the underlying endpoint (GET /billing/subscription). It distinguishes itself from the 20 sibling tools by focusing on billing/usage rather than templates, webhooks, or sends. This is a specific verb+resource definition.

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 this tool is for checking billing/usage context, but it does not explicitly state when to use it vs. alternatives like whoami or list_* tools. It also doesn't mention that it's a zero-parameter call that gives account-level info. The context of when to check usage vs. other endpoints is left to the agent's inference.

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