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

Annotations give the safety profile (readOnly, openWorld, non-destructive, non-idempotent), and the description adds genuinely useful context beyond them: results are ranked by live health/speed/price, fallbacks are returned when sellers overlap, and the payment model ('you pay the seller directly; SwitchBord never touches money') clarifies an otherwise ambiguous transaction boundary. The 'right now' wording also helps explain the non-idempotent hint.

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?

Front-loaded with the core purpose and three tight sentences with no filler. The payment-model sentence is the least essential but still earns its place by resolving who pays whom.

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, the description carries the return-value burden and does so reasonably: ranked sellers, fallback behavior when no group matches, and the payment flow. What is missing is any sense of the result shape or how many items come back, but for a discovery tool this is close to sufficient.

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 coverage is 60%: task, market and accepts carry schema descriptions while limit and max_price_usd do not. The description loosely ties to max_price ('ranked by ... price') and to market ('group of sellers') but adds no syntax or format detail, so it neither compensates for the gap nor undercuts the schema.

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?

Names a specific verb and resource (find paid API endpoint) scoped to a task, and the parenthetical 'x402 / MPP' identifies the domain precisely. It does not explicitly distinguish itself from siblings list_markets and report_result, though the discovery-vs-listing distinction is inferable from the title.

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?

The 'Works for any task' phrasing implies broad applicability and the fallback sentence explains edge behavior, but there is no explicit when-to-use/when-not statement and neither sibling is named. An agent must infer that list_markets is the browsing counterpart.

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