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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: accounts without linked scenarios return no data, forecast horizon is bounded by subscription plan date limits, credit-card balances are naturally negative, and long horizons should use monthly resolution to keep responses manageable. These are exactly the non-obvious traits an agent needs before calling.

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?

Sentences are dense and front-loaded with purpose before caveats. A few points (monthly resolution for long horizons, account-type list) are duplicated by the schema descriptions, which is modest redundancy rather than noise.

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 six-parameter, zero-required read tool with no output schema, the description covers purpose, data-availability caveats, parameterization heuristics, and the paired navigation tool. Return-value shape is only gestured at ('shows where each account is heading', danger zones) rather than described, which keeps it short of a 5.

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 the baseline is 3. The description adds cross-parameter meaning the schema does not: danger_threshold must be adjusted for credit accounts because their balances are naturally negative, and resolution should be monthly for long horizons. That is real semantic value beyond field-level docs.

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 a specific verb and resource — forward-looking account-level balance projections — with a scope qualifier ('account-level') that implicitly separates it from the aggregate net_worth_forecast sibling. It also states the secondary output (danger zones). It stops short of explicitly naming the sibling it is not, which keeps it from a 5.

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 concrete usage context: filter by account types/IDs, use monthly resolution for long horizons, adjust danger_threshold for credit cards, and pair answers with navigate_to_cashflows. There is no explicit 'use this instead of net_worth_forecast/trend_analysis' routing statement, so the alternatives dimension is only implied.

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