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 paywall, the x402 payment-instruction return path, newest-first ordering, and that 200 is a hard cap rather than a page of a larger set. It omits rate limits, refresh cadence, and whether payment is per-call or cached.

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?

Three short sentences, front-loaded with the paywall warning and the hard-cap caveat that an agent most needs. 'Returns x402 payment instructions to call /api/x402/firehose' is slightly compressed but earns its place.

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 zero-parameter, no-output-schema feed, the description covers the return fields, ordering, cap semantics, and the payment flow. Only the mechanics of the paywall (cost, per-call vs. cached, retry behavior) remain thin.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly implies no filtering or pagination inputs exist.

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 ('Returns the 200 most recent trades across all X1 tokens, newest first') and enumerates the payload fields, so the agent knows exactly what data comes back. It doesn't differentiate itself from similar siblings such as recent_trades or arc_trades, so it stops short of a 5.

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 'PAYWALLED' prefix and the note that it returns x402 payment instructions imply how to proceed, but there is no explicit statement of when to choose this over recent_trades, arc_trades, or arc_whale_feed, nor any guidance on cost or whether payment must be repeated per call.

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