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

Beyond the annotations (which already declare readOnly/idempotent/non-destructive), the description discloses ordering ("oldest first"), normalization ("MRR x12"), error behavior ("Unknown slug -> isError"), and a concrete rate/cost profile ("free, 100 calls/day without a key"). These are non-obvious operational facts an agent needs before deciding whether to call or fan out.

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 trigger condition and core behavior are front-loaded in the first two sentences, and the example plus cost note are compact and useful. The parenthetical field list and nested parentheses make the final sentences denser than necessary, though nothing is truly wasted.

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?

An output schema exists, so return values need no full prose explanation, and the description still covers ordering, normalization, error handling, and cost. For a one-parameter read-only tool this is everything an agent needs 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 coverage is 100% and the single parameter is already documented, so baseline would be 3. The description adds value by supplying a concrete example mapping {"slug":"lovable"} to Lovable's ARR points and by defining the failure case for an unrecognized slug, which the schema does not state.

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 states a specific verb+resource: it returns one business's dated revenue series, and it names the triggering user intent ("how fast an AI company grew or for its revenue over time"). The phrase "one business's" implicitly separates it from siblings like compare_businesses and benchmark_business, so an agent can route without opening a schema.

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 gives an explicit trigger condition ("Use when the user asks how fast an AI company grew or for its revenue over time"), which is clear context for selection. It does not explicitly name or exclude the alternatives (compare_businesses, get_business), so the agent must infer the boundary from "one business".

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