call_service

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

The description adds significant behavioral context beyond annotations: it spends real money, is non-idempotent, has external side effects, returns upstream response verbatim, handles 402 as normal result, and requires specific env var. No contradictions with annotations.

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 description is well-structured with sections (PRECONDITIONS, BEHAVIOR, Returns) and is front-loaded. Every sentence adds value, though it could be slightly more concise without losing meaning.

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 complex tool with paid calls, external side effects, and preconditions, the description covers preconditions, behavior, error handling, idempotency, and return format. It lacks rate limits but is otherwise comprehensive.

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 baseline is 3. The description adds meaningful context like serviceId must come from list_services, idempotencyKey for safe retry, and body only for certain methods, enhancing understanding beyond the schema.

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 clearly states the tool invokes an upstream API service through a pay-per-call proxy, specifying the verb and resource. It distinguishes itself from sibling tools (check_balance, check_tax, etc.) by focusing on paid external calls.

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 provides PRECONDITIONS (env var, serviceId from list_services) and explains that 402 responses are returned normally for autonomous stop. However, it does not explicitly state when not to use the tool or compare directly with siblings, though sibling names imply differentiation.

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