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

Adds real context beyond the annotations: 'status' reads from the database and makes no Stripe call, while 'upgrade' and 'manage' return links rather than performing the mutation themselves, which explains why readOnlyHint is false despite the agent never directly changing billing. 'Free' hints at no cost/quota impact, though it is too terse to be unambiguous. No contradiction with the 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?

Extremely compact, action names front-loaded, each fragment carries distinct information. The telegraphic dash style and the dangling 'Free.' cost a little clarity but there is no wasted sentence.

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 2-parameter tool with no output schema, the description usefully characterizes return values (status data vs. links) across all three actions, which the schema cannot convey. It stops short of noting what 'status' contains in detail or any failure modes, but nothing essential for invoking it correctly is missing.

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%, so the schema already documents both 'action' (with enum) and 'plan' (with the 'solo' example). The description explains what each action yields but never mentions the 'plan' parameter or when it is required, so it adds no meaning over the schema; baseline 3 applies.

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 enumerates all three modes (status, upgrade, manage) and what each produces, so an agent can identify the tool's scope as plan/billing management. It never states an overarching verb+resource in sentence form and does nothing to differentiate from siblings like 'usage', but the per-action breakdown is specific enough to act on.

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?

Mapping each action to a need (plan/usage info, checkout link, card/invoices/cancellation) implicitly tells the agent which action to pick, which is the main routing decision for this tool. There is no explicit when-to-use/when-not wording, no mention of prerequisites, and no alternative tool named.

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