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

With no annotations, the description fully covers key behaviors: the HTTP-402 price challenge, the fact that free endpoints don't issue 402 and return a $0 response on dry run, and that calls above $10 are refused. This is critical safety information for an agent spending user balance.

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 sentences, each dense with actionable information: the core purpose, the dry-run workflow, the free-endpoint edge case, and the pricing ceiling. No redundant phrasing.

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?

Given 7 parameters, no annotations, and no output schema, the description covers the essential behavioral mechanics and execution workflow. It doesn't describe the response shape for paid calls or failure modes like insufficient balance, but it does mention the dry-run response at $0, leaving only 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 the baseline is 3. The description adds meaningful context beyond the schema by explaining how dry_run interacts with the 402 challenge and how max_amount_usd tightens the $10 ceiling. The schema already handles per-parameter semantics well.

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?

The description opens with 'Call one of the discovered endpoints and pay for it from the user's balance', which clearly defines the verb, resource, and transactional nature. This distinguishes it from sibling tools like discover and balance.

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?

It provides explicit workflow guidance: 'Set dry_run: true first to read the real price... Repeat the identical call without dry_run to execute it.' It also references 'discovered endpoints', implicitly positioning it after discover, and explains the default $10 ceiling with max_amount_usd as a tightening option.

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