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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds substantial behavior beyond them: the x402 payment flow (call once with no payment_header to get the challenge, then pay from the caller's own wallet), the flat $0.10 USDC pricing, the no-wallet custody model, and the crucial semantic that N counts stored editions, not calendar days. This is rich context an agent genuinely needs.

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 paid marker and the core situation, and every claim is substantive. Slightly repetitive, though: flat pricing is stated three times ('one flat price', 'flat-priced regardless of count', '$0.10 USDC on Base') and the no-wallet clause appears in both description and schema.

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?

No output schema exists, yet the description tells the agent the return shape (one full brief per date, oldest first) and fully documents the payment handshake. For a paid, 2-parameter archive tool, an agent has everything needed to call it correctly on the first and second attempt.

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 baseline is 3, but the description adds real meaning beyond the schema: it clarifies that 'days' counts stored editions rather than calendar days and that returned dates can therefore span more than N days, plus points to /health archive_dates for the available dates. That is value the schema's own wording does not fully deliver.

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 specific verb and resource: retrieving the last N stored Daily Agent Signal editions (1-30), oldest first, one full brief per date. It explicitly differentiates itself from sibling tools signal_latest, signal_day, and signal_continuity, so an agent can route without opening another 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?

Explicitly names when to use it ('several recent days at one flat price') and when not to, with the exact alternative for each rejected case (signal_latest for the most recent edition, signal_day for one past date, signal_continuity for thread persistence without full text). Nothing is left to inference.

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