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

Beyond readOnlyHint and openWorldHint, the description discloses zero cost, no Source calls, the valid=false refusal payload (status, code, fix sentence), the valid=true payload (total, perLeg, balance), and the estimateToken required by explore. No behavioral surprises are left hidden.

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 core purpose is front-loaded and the workflow is clear. However, the final sentence largely repeats return fields already listed in the valid=true sentence, and 'without calling any Source' appears twice. Still, relative to the schema complexity, it is reasonably tight.

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 full burden of explaining return values and failure modes. It covers both valid branches, the zero-cost/no-Source behavior, and the next step of passing estimateToken to explore. Nothing essential is missing for an agent to call it correctly.

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 schema already documents the two parameters and all nested fields. The description adds the useful relationship 'arguments of explore, minus the token,' but no per-parameter semantics beyond the schema. Baseline 3 is appropriate.

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 opening phrase 'Price an Explore run without calling any Source' names a specific verb, resource, and scope. It also distinguishes itself from the sibling explore tool by saying it takes 'the arguments of explore, minus the token' and later passes estimateToken to explore.

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 description clearly frames when to use it: before running an explore, to show the person the cost, then pass estimateToken to explore. It also notes it costs 0 credits and calls no Source. It does not explicitly enumerate when not to use it or contrast with other estimate siblings like query_estimate, so it stops short of a 5.

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