Builder Journey

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

Even though annotations already establish readOnly/openWorld/idempotent behavior, the description adds substantial non-obvious behavioral details: fixed minFills=3, trailing-year cohort construction, per-wallet aggregation, truncation bias in young cohorts, dataNotes in the response, and slow/cached first call. This goes well beyond what annotations provide.

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 dense and run-on in places, but every sentence carries meaningful information: metrics, cohort definition, caveats, use case, tier, and performance. It is front-loaded with purpose and needs to be long because there is no output schema to document the return values.

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 metric-heavy tool with no output schema, the description is remarkably complete: it defines the universe, the per-wallet computation, all metric names, the bias caveat, the comparison tool, required tier, and call behavior. An agent has enough context to invoke it correctly and interpret the response.

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 3. The description adds value by clarifying that builder is the only substantive analytical parameter ('no other parameters') and explaining the cohort semantics tied to that address. It does not add much about useToonFormat beyond the schema, but schema already covers it 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 a specific analytical question ('how fast and how unevenly does builder X monetize a new user?'), names the exact resource (a builder's trailing-year acquisition cohort), and enumerates concrete metrics. It explicitly differentiates itself from builder_lifecycle, making sibling confusion unlikely.

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 gives an explicit use case in quotes, explicitly says what it is NOT ('NOT the lifetime user base builder_lifecycle covers'), and provides operational guidance such as Pro tier requirement, ~90 second first-call latency, caching, and retry on timeout. This fully equips an agent to decide when to call it.

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