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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is fully covered. The description adds value by enumerating what the model returns (useful since there is no output schema). It does not disclose what happens when optional inputs (gross_margin_pct, value_per_conversion) are omitted — presumably profit/ROAS/break-even outputs degrade or disappear — nor whether results are monthly or annual.

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?

A single dense sentence that front-loads the verb and the input contract, then lists outputs. No filler, though the output enumeration is long relative to the near-total absence of usage guidance — the space allocation is slightly off.

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?

With no output schema, listing the computed metrics is necessary and present. But for a 6-parameter financial model the description leaves key gaps: the meaning of omitted optional inputs, the time period of the forecast (monthly implied only by the parameter name), and how it differs from sibling forecasting/ROAS tools.

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 67%, and the description only names three inputs (budget, CPC, conversion rate), ignoring currency, gross_margin_pct and value_per_conversion entirely. The optional two are the ones that change which outputs are computed, so their role deserves a sentence and the default INR currency is never mentioned. The description adds little beyond what the schema's own field descriptions already say.

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 verb ("Forecasts") with a concrete resource (paid search or social budget) and enumerates the outputs produced: clicks, conversions, CPA, revenue, ROAS, profit, break-even CPA. An agent can tell this is a modeling/calculator tool rather than a live-data read. It does not, however, distinguish itself from overlapping siblings such as roas_check, ad_budget_planner, break_even or max_affordable_cac.

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?

Usage is only implied by the stated inputs (budget, CPC, conversion rate) — an agent can infer this is a what-if projection rather than a measurement. There is no explicit when-to-use guidance and no mention of the sibling tools it overlaps with (ad_budget_planner, roas_check, max_affordable_cac), which is a real risk given the crowded calculator family.

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