Get a month’s budget

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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantive behavior beyond that: amounts are integer cents, spending is negative, carryover flag is present, and income categories behave differently (money tracked as `received`, budgeted/spent/balance zeroed). The warning never to report an income category as '0 spent' is exactly the kind of domain nuance an agent cannot infer from structure.

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?

Front-loads the summary of returned data before the income-category caveat, and every sentence carries information. The second paragraph is dense but justified, as it prevents a real misinterpretation; only marginally longer than strictly necessary.

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 carries the full burden of describing return values, and it does so thoroughly — totals, per-category fields, units, sign convention, and the income-category exception. Nothing an agent needs to interpret the result is missing.

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 100% and the single `month` parameter is fully documented in the schema as YYYY-MM. The description adds no format or constraint detail beyond what the schema already provides, so the baseline 3 applies.

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 and resource ('Read one month's budget') and enumerates exactly what the response contains: totals, per-category budgeted/spent/balance, and the carryover flag. An agent can distinguish this from list_budget_months (enumeration) or set_budget_amount (mutation) without inspecting the schema.

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?

Explicitly frames the use case with 'This is the tool for "am I over budget?"', giving a clear scenario for selection. It does not, however, name an alternative tool or state when not to use it, so it falls short of full routing guidance.

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