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

Annotations already cover read-only, idempotent, and non-destructive traits. The description adds valuable edge-case behavior: 'Empty books return a structured empty object (has_data: false), not an error.' This is beyond the annotations and helps agents handle empty responses gracefully.

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?

The description is three short sentences, each contributing essential information: overall purpose, expected output type, and the empty-book edge case. No redundant phrasing or unnecessary details.

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?

The tool is a read-only getter with fully described parameters and clear annotations. The empty-case behavior is a useful addition. However, the return structure for non-empty results is only generally described ('shows what revenue/expenses are expected'), which is acceptable given no output schema and the tool's relative simplicity.

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 schema fully documents all three parameters. The description's mention of 'revenue/expenses' provides slight context for the account_name filter, but it does not add substantial semantic value beyond the schema.

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 clearly states the action and resource: 'Get projected future values from financial forecasts.' It specifies that it shows expected revenue/expenses, which distinguishes it from actuals-focused siblings like get_actuals_vs_budget. The scope is unambiguous.

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 the tool is for retrieving forecasted financial data, but it does not explicitly state when to use it over alternatives or mention any exclusions. An agent must infer usage context from the phrasing, which is adequate but not fully explicit.

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