Get Custom Costs

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

The readOnlyHint annotation already establishes the read-only nature, and the description adds behavioral context about the date-window filtering and recurring-cost edge case. No contradiction exists, and the extra context is valuable.

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?

Two sentences with an action-first verb, concrete examples, and a clear use case. No redundancy or filler, making it appropriately sized and front-loaded.

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 simple read tool with full schema coverage and no output schema, the description covers purpose, examples, and use case. It does not mention pagination behavior, but that is available in the schema and not critical for this tool.

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 descriptions cover 100% of parameters, including detailed semantics for fromDate. The description mentions 'date window' but does not elaborate on individual parameters, so it adds minimal value 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 description opens with 'List custom costs', a specific verb and resource, and adds clarifying examples (agency fees, tool subscriptions, offline spend) and a date-window scope. This clearly differentiates it from sibling tools like get_calls or get_leads.

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 second sentence gives explicit use-case guidance: 'Use this to audit costs that skew profit and ROAS, especially recurring ones left without an end date.' It lacks explicit alternatives or when-not-to-use, but the context is clear.

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