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

Annotations already declare a read-only, idempotent, closed-world, non-destructive operation, but the description adds substantive behavioral context: the two bases must not be summed, only whole_government yields surplus/deficit and net debt, results are sorted largest-difference-first, and every figure carries a source link. It stops short of describing pagination or error behavior, but the added disclosure is well beyond what the annotations provide.

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 most important content (what is returned, the two non-additive bases, the default-year rule) is front-loaded, and the dense single paragraph is information-rich rather than padded. It is slightly long and would benefit from breaking the data-base caveat into its own sentence, but every clause carries weight.

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 and two optional parameters, the description carries the return-value burden and does so well: it enumerates the returned quantities and explains the two reporting bases and their limitations. It omits return format and error/degenerate cases, but for a read-only reporting tool the agent has enough 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%, so both parameters (year, department) are already documented, and the description's note on omitting year and the partial-name matching for department largely restates the schema. It adds the ordering of department results ('largest difference first'), which is a useful but marginal addition over the schema baseline.

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 resource and enumerates exactly what is returned: budgeted vs actual spending, the difference, surplus/deficit, net debt, and per-department comparisons. It also distinguishes its two underlying data bases (modified cash Estimates vs audited Public Accounts), which lets an agent understand the tool's scope without opening siblings.

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 an explicit usage rule ('Leave out year for the latest year with published results') and the temporal boundary (years from 2019-20; newest budgets have no results yet). It does not compare against sibling tools like get_totals or get_department, so it falls short of naming alternatives.

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