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

With no annotations, the description carries the full burden. It usefully discloses a cost constraint (1 credit per call) and the computed outputs, but says nothing about statelessness, behavior when no inputs are supplied (all 7 params are optional), or error handling. The credit disclosure is genuine added value beyond structured fields.

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 tight sentences, front-loaded with the core compute capability and followed by the projection feature and cost. No filler; every clause carries information.

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 7-parameter calculator with no output schema and no annotations, the description covers the output metric set and the projection behavior well. Remaining gaps are the unmentioned profit_margin_percent input and the all-optional-input edge case, which are modest given the tool's simple deterministic nature.

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 only 14% (only new_budget is documented), so the description must compensate. It names five of the seven inputs and conveys an important semantic the schema cannot express ('any mix' — all params optional and combinable), but it never mentions profit_margin_percent or which input combinations yield which metrics.

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?

States a specific computation verb and enumerates the exact metric set (CTR, CPC, CPM, conversion rate, CPA, ROAS, ROI, break-even), plus the projection capability. This clearly separates it from sibling calculators like ab_test_calc or tempo_calculator without needing schema inspection.

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 implies usage by listing accepted inputs ('from any mix of spend, impressions, clicks, conversions and revenue') and the projection feature, but gives no explicit when-to-use, when-not-to-use, or alternative-tool routing. Usage must be inferred from the metric list.

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