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

Annotations already establish readOnlyHint=true, and the description adds non-obvious behavior beyond that: credit limits are subtracted when the user's includeCreditLimitInStats setting is on, and the returned amount is denominated in the base currency. It even sketches the return shape since no output schema exists.

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: purpose and return shape first, a conditional behavior second, and sibling routing last. No filler or restatement of the tool name.

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 present, the description compensates by naming the returned fields (amount, currencyCode, date) and their meaning. For a single-parameter, read-only aggregate tool, an agent has everything needed to call it 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 coverage is 100% and there is only one parameter, whose YYYY-MM-DD format is fully documented in the schema. The description clarifies that date is the as-of date for an aggregate across all accounts, but adds no syntax or constraint detail beyond the schema, so 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 with scope: 'total balance across all accounts on one date'. It also distinguishes itself from get_balance_history by naming the point-in-time vs. series distinction, so an agent can route without opening either 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 routes the time-series case to get_balance_history, which is the main ambiguity among siblings like get_net_worth_history and get_cumulative_stats. It does not cover other edge cases (e.g., which accounts are excluded), but the primary alternative is named with its selecting condition.

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