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

Annotations already declare readOnlyHint/idempotentHint, but the description adds real context beyond them: the required account:read scope, an explicit statement that it cannot charge or manage billing, and a post-checkout re-verification workflow. The remaining gap is that it doesn't clarify what the 'human payment handoff' actually returns.

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 sentences, front-loaded with the resource list, then permissions, then the workflow. The 'Read-only: cannot charge or manage billing' clause partly echoes readOnlyHint, but it still earns its place as a reassurance against a billing-sounding name.

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?

With no output schema and no parameters, the description carries the burden of describing returns, and the opening list of plan/usage/billing/spend-cap/pricing largely does. The vague 'human payment handoff' is the one element an agent may not be able to act on precisely.

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 there is nothing for the description to disambiguate; baseline 4 applies. No parameter-level meaning is missing.

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 names a specific verb (Read) and enumerates the exact resources returned: account plan, usage, billing estimate, spend cap, Pro pricing, and payment handoff. No sibling tool touches account/billing scope, so the purpose is unambiguous without opening the schema.

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?

It gives clear conditional guidance: call again after checkout to verify hosted entitlement, then retry the original task, and invoke for a payment handoff 'when needed'. It stops short of naming an explicit alternative or exclusion, but the workflow context is concrete.

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