custom_report

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

Annotations mark this as readOnlyHint=true and openWorldHint=true, and the description adds substantial behavioral context beyond them: it returns raw JSON, auto-windows custom ranges into 1-year chunks back to a 2023-06-01 floor, and warns that filters are 'You own its correctness.' This makes the tool's behavior and limitations clear to the agent before invocation.

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 compact, front-loaded with the core purpose, and every sentence earns its place: what it runs, what it returns, and when to use it. There is no filler or repetition of schema details.

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 high-complexity 12-parameter tool with no output schema, the description covers the essential invocation context: raw JSON output format, custom range chunking and floor, and the escape-hatch use case. Combined with the fully described schema and read-only annotations, nothing critical is missing for correct selection and use.

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 coverage is 100%, so the baseline is already 3. The tool description adds cross-parameter meaning by explaining that custom ranges are auto-windowed, start overrides timeframe, and raw filter expressions are the caller's responsibility. This goes beyond simply restating property names and helps the agent combine parameters correctly.

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 'Expert escape hatch - run ANY Klaviyo values or series report,' naming a specific verb, resource, and scope. It clearly distinguishes itself from specialized report tools by emphasizing full control over statistics, group_by, filter, interval, and timeframe, so an agent can tell this from siblings like campaign_report or flow_report.

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 explicitly states when to use this tool: 'Use when the specialized report tools do not expose a statistic, dimension, or filter you need.' This gives both a positive use case and an implicit exclusion, pointing the agent to specialized alternatives when they suffice.

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