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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety is covered. The description adds meaningful context beyond them: what the landed page displays (progress bars, surplus/deficit, rollover, per-category table) and the constraint that it lands on the whole budget with no single-category filter. It doesn't cover return payload or how params alter the rendered page, keeping it off a 5.

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-loaded with the destination and scope, then examples, then alternatives. The run of example questions is helpful but slightly padded; still, every clause is relevant and nothing is filler.

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 navigation tool with no output schema, rich annotations, and 100% schema coverage, the description supplies what an agent still needs: what page is reached, what it shows, and how it differs from adjacent navigations. Nothing required to select or call it correctly 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 description coverage is 100%, so all seven parameters (roll_up, date ranges, inherit_date_range, include_uncategorised, include_rollover_amounts) are fully documented in the schema. The description adds no parameter-level guidance beyond what the schema states, 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 action (deep link to the Budget page at /budget), the resource, and the scope (ONE period, whole budget with no single-category filter). It explicitly names sibling navigations it is not (navigate_to_trends, navigate_to_income_expense), so an agent can disambiguate without opening schemas.

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?

Gives concrete triggering asks ('am I on budget this month', 'how much is left in my grocery budget') plus explicit alternatives with the condition that selects them (trends over time, actual-vs-budget read-out). When-to-use and when-not are both covered.

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