ForecastCashFlow

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

Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds meaningful behavioral context beyond that: the forecast derives from current balances plus scheduled transactions only, and explicitly omits unscheduled spending, which is exactly the kind of limitation an agent needs to know.

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 tight sentences, front-loaded with the core action and scope, followed by the output summary and the key limitation. No filler and no repetition of schema content.

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 an output schema present, return values need not be re-explained, and annotations cover the safety profile. The description supplies the forecast basis and its exclusion, which is everything an agent needs to decide and call 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 description coverage is 100%, so all three parameters (days, plan_id, account_id) are already fully documented. The description's "next N days" phrasing adds nothing beyond the schema's "1-365" range. Baseline 3 is appropriate when structured fields carry the semantics.

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 uses a specific verb ("Project") with a clear resource ("account balances") and states the mechanism (current balances + scheduled transactions). It is distinguishable from neighbors like Ynab_FindOverspending or Ynab_SummarizeSpending, which look backward at past spending rather than projecting forward.

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 scope note "Doesn't include unscheduled spending" implies when the tool is appropriate, but no sibling tool is named and no explicit when-to-use/when-not guidance is given. Usage must be inferred from the description's framing.

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