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

Annotations already declare read-only, idempotent, open-world behavior, and the description adds genuinely non-obvious context: this is a metered call at $0.08 USDC, payment credentials must travel in headers (X-Payment / X-Payment-Tx / Authorization: Bearer fg_…) rather than arguments, and results are limited to the comparison table. It stops short of describing caching, rate limits, or response shape, which keeps it below 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?

The English preamble is well front-loaded and high value, but the payment and no-args information is then repeated verbatim in a bilingual zh/en block, roughly doubling length without adding new information for a single caller. Structure is serviceable but the redundancy costs it.

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 burden of describing returns and does so by enumerating the five matrix columns. Payment mechanics and the tier boundary are also covered, leaving only minor gaps around result format and any usage limits.

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 schema has zero parameters, which sets the baseline at 4. The description reinforces this with an explicit 'Args: none' and instead directs where authentication must go, preventing a common error of stuffing payment fields into the argument object.

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 deliverable: a one-call matrix of 10 major exchanges covering tier, official fee stance, real token budget, review timeline, and requirement count. It answers the framing question ('which exchange is cheapest to list on') and explicitly scopes itself as the entry tier versus the $0.50 single-exchange deep dive, so an agent can distinguish it from deeper listing-intel siblings.

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 opening question ('which exchange is cheapest to list on') gives a clear triggering scenario, and the tier note tells the agent when to step up to the paid deep dive. It does not, however, say when to prefer this over sibling tools like exchange_overview or listing_intel, so the alternative-selection guidance is only partially covered.

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