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

Adds real context beyond the annotations: it discloses the per-domain credit cost, the plan-vs-credit distinction, and token lifetime until expiry or credit exhaustion. The readOnlyHint=false is consistent with a call that consumes purchased credits. Missing are failure semantics (invalid/expired token, zero balance) and any note on what a successful response contains.

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 four sentences are individually tight, but the ordering is wrong for selection: it opens with a token plumbing instruction instead of what the tool returns. Cost and plan rules come after, which an agent scanning for purpose may never reach.

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 9-parameter, credit-consuming tool with no output schema and minimal annotation detail, the description covers the commercial contract (credits, plans, token reuse) but leaves parameter-to-operation mapping and return shape entirely unspecified. An agent can authenticate correctly but will likely mis-bind parameters on the first call.

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 only 11%: accessToken is the lone documented parameter, and the description merely restates that it comes from mpp-purchase. The other seven parameters (domain, operation, since, country, technology, liveOnly, offset, minimumMonthlySpend) get no meaning, no required/optional pairing with each operation, and no format hints. With such low coverage the description should compensate heavily and does not.

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 never states the tool's purpose directly; the resource only emerges obliquely from 'Domain and change lookups' and 'Lists'. The lead sentence is about authentication ('Use the temporary access_token returned by mpp-purchase'), so an agent must infer that this is the paid data-retrieval endpoint for domains, changes, lists and balance.

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 clearly routes the agent from mpp-purchase to this tool and states the precondition that lists need a basic/pro/team plan rather than lookup credits. It doesn't say when to prefer this over the plain domain-api/list-api siblings, but the paid-vs-free distinction is at least implied by the credit language.

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