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

With no annotations, the description carries the full burden and does well: it discloses the price ($0.05 in USDC on base via x402), that no account or API key is needed, the two-step payment handshake, the hourly rebuild cadence, the 30-day window cap, and that every buyer gets an identical, flat-priced response. It does not cover failure modes (e.g., what happens if payment is rejected) or rate limits, keeping it just short of a 5.

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: the first sentence answers 'what does this return' before any pricing mechanics. The pricing/determinism paragraph is somewhat verbose and the 'first or hundredth' clause is closer to marketing than operational guidance, but nothing is confusingly ordered or badly buried.

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 paid, output-schema-less data endpoint with no annotations, the description covers cost, auth-free access, the payment workflow, freshness, and the qualitative shape of the result (started/stopped services plus index-wide totals). It stops short of describing the actual response structure, but an agent has enough to invoke it correctly.

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%, so the schema already documents both `days` and `payment`, making 3 the floor. The description adds real meaning beyond the schema by explaining the x402 two-call protocol and framing `days` as a user-chosen window, which clarifies how the optional `payment` param is actually used.

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 sentence states exactly what the tool returns — services that started and stopped answering across the whole index — and the follow-up ('Services that started answering and services that stopped, with index-wide totals') removes the metaphor's ambiguity. It is clearly distinguished from narrow siblings like gone_dark and new_services because it covers both directions of change plus index-wide totals.

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 description gives explicit procedural guidance for payment ('Call without `payment` to receive the exact payment requirements, then call again with `payment` to be served') and a window constraint (up to 30 days). However, it never says when to prefer this tool over alternatives such as gone_dark, new_services, or has_it_changed, which is the more important selection guidance.

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