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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description's 'Comparing is read-only and changes nothing' largely restates that. It does add the constraint that comparison happens in a single currency, but it does not say what happens when scenario_ids is omitted or how many scenarios can be compared at once.

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?

Three short sentences, front-loaded with what is compared and what is returned, with no filler. The final sentence partially duplicates the readOnly annotation, which is the only wasted space.

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, the description usefully enumerates the returned metrics (income, spend, profit, profit gap), which is exactly what an agent needs. The main gap is the unspecified behavior when scenario_ids is empty, which matters for a tool with zero required parameters.

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%, with period and currency already documented in the schema. The description reinforces the single-currency constraint but adds nothing about scenario_ids semantics (e.g., whether omitting it compares all scenarios) or the period default, so it does not compensate for the remaining coverage gap.

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 names the resource (what-if scenarios vs. the base forecast) and enumerates the outputs (income, spend, profit, profit gap), which is far more specific than the title alone. It does not explicitly name a sibling tool, but the phrase 'once the scenario exists' implicitly separates it from fin_create_scenario.

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 a concrete usage context ('what happens if sales drop 15% for three months') and states the prerequisite that the scenario must already exist, which routes the agent to fin_create_scenario first. It stops short of explicit when-not guidance or naming alternatives directly.

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