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

With no annotations, the description carries the burden and does it well: it discloses the 1 CRD cost per call, that the charge applies even on rejection, that a 429 RATE_LIMITED is free, and that errors carry a request_id for support escalation. It omits return ordering/pagination behavior, which keeps it 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?

Three tight sentences, no filler: payload fields first, filters second, cost/error behavior last. The parenthetical field list is dense but each item earns its place, and the cost caveat is stated precisely rather than hedged.

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 six-param read tool with no output schema, the description compensates by naming the returned fields and describing the billing and error contract, which is the information an agent most needs before spending credits. It stops short of covering result ordering, pagination, or what an inactive pair looks like, leaving minor gaps.

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 all six parameters are already documented, and the description only restates the source/target credit-type filters without adding format or semantics. include_inactive, api_key, project_id, and x402_payment are left entirely to the schema, which is appropriate but adds no extra meaning.

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 ("List credit swap pairs") and enumerates the fields returned, so an agent knows exactly what it gets back. It never names the sibling it pairs with (execute_swap) or says when to list vs. swap, so sibling differentiation is implied by the name rather than stated.

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?

"Optionally filter by source or target credit type" gives a light usage cue for the two filter params, and the cost warning implicitly discourages speculative calls. There is no explicit when-to-use/when-not guidance relative to execute_swap or list_credit_types, so usage is only implied.

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