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

annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered upstream. The description adds genuinely useful context—no card, no KYC, accepted chains (USDC on Base/Solana/Ethereum), and that a human principal owns billing—but says nothing about the shape of the response or whether prices are static.

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 purpose is stated first, which is good, but most of the body is enumerating dollar amounts and trial terms that are almost certainly the tool's output rather than invocation guidance. Those sentences are informative but belong to return values, not to the selection decision.

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 must convey what comes back, and it does so by listing the tiers, the Action Gate plan, and the trial conditions. An agent can call it confidently, though the mismatch with sibling 'meter_pricing' is never resolved.

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 schema has zero parameters, establishing a baseline of 4. The stray '(plan=action)' notation hints at a filter argument that does not exist in the schema, which is mildly confusing but does not offset the fact that no parameter documentation is needed.

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 opening clause 'List Agent Control plans and trial truth' gives a specific verb and resource, so an agent knows this returns plan/pricing catalog data. However, it never distinguishes itself from the sibling 'meter_pricing', leaving ambiguity about which pricing tool answers which question.

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?

There is no statement of when to call this versus 'meter_pricing' or 'start_trial', both of which appear adjacent in the sibling list. Usage is only inferable from the content itself, which is pricing facts rather than invocation guidance.

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