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

Annotations already declare idempotentHint=true and destructiveHint=false, so 'safe to call repeatedly' largely restates structured data, though it usefully reinforces polling. The description does add what the call yields (new balance and plan), which is valuable given there's no output schema. It does not disclose the important behavioral cases for a payment-confirmation tool: pending/unpaid state, failure handling, or why readOnlyHint is false despite framing this as a 'check'.

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?

A single compact sentence that front-loads the prerequisite, then the action, then the payoff. Nothing redundant or padded.

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?

Without an output schema, the description does convey the return shape (balance and plan), which is a real contribution. However, for a polling-style payment verification tool the key unknown states (not yet paid, failed, expired session) are unaddressed, leaving the agent unsure how to interpret a non-success result.

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% and the single session_id parameter is fully documented there, including the cs_ prefix, so the schema already does the work. The description adds no parameter guidance of its own; 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?

States a specific verb and resource ('check payment' / confirms payment went through) plus what it returns (new wallet balance and plan). It also names the two sibling tools that produce the prerequisite (spur_top_up_wallet, spur_change_plan), so an agent can place it in the billing flow without ambiguity.

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?

Explicitly states the triggering condition: call it after the user pays a Stripe checkout link from spur_top_up_wallet or spur_change_plan. 'Safe to call repeatedly' further implies a polling pattern. It doesn't state what to do if the payment is still pending or how long to wait, so it stops short of full when/when-not guidance.

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