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

With no annotations, the description carries the full burden and does: it discloses that the tool is paid ($0.50 USDC), the 402 payment handshake, an auth bypass, UTC defaulting, and that the response is items-only with no prose. These are the behavioral traits an agent cannot infer from the schema.

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?

Four short sentences, front-loaded with what the tool returns and why, followed by the payment mechanics. No filler, and each sentence carries a distinct fact.

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?

An output schema exists, so return values need no prose explanation; combined with full parameter coverage and the payment/auth disclosure, an agent has everything needed to call this correctly, including on the 402 retry path.

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 100%, so the parameter baseline is 3, but the description adds real value: it explains payment_tx as the field supplied on re-call after a 402 and confirms the date defaults to today UTC. Only agent_id is left to 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?

States a concrete verb and resource ('Get the top 5 signals from today's brief as structured JSON') and immediately frames it as a cheap sample of the sibling tool daily_brief, which lets an agent distinguish the two without reading either 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?

Gives an explicit selection criterion — call this to 'decide whether to buy the full brief' — and names daily_brief as the alternative. It also documents the exact 402 recovery path (pay the returned memo, re-call with the same args plus payment_tx) and the bearer-key bypass.

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