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

Annotations already declare readOnlyHint=true, destructiveHint=false and closed-world scope, so the safety profile is covered. The description's genuinely additive contribution is the unit convention (currency units, not cents), but it says nothing about how empty categories or ledgers with no activity are represented, which matters for a summary tool with no output schema.

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?

A single front-loaded sentence with no filler; the parenthetical unit clarification earns its place. It is arguably too terse given the undocumented ledger_id, but nothing is redundant.

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 two-parameter read-only summary with annotations covering safety, the definition is minimally adequate, and the units note is important. It stops short of explaining the undocumented ledger_id or what the 'category budgets' portion contains.

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 50%: the month parameter has its own pattern and a note about year-less months in the schema itself, while ledger_id is a bare integer with no explanation anywhere. The description does not compensate for that gap, and its 'ledger-month' phrasing only loosely links the two required inputs.

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 resource and scope: total spend plus category budgets for exactly one ledger-month. It implicitly distinguishes itself from multi-month and breakdown siblings by the single-month framing, but never names an alternative to sharpen the boundary.

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?

Usage is only implied through the 'one ledger-month' scope; there is no explicit when-to-use, no when-not-to-use, and no pointer to get_category_breakdown, get_budget_outlook or get_last_n_months_summary for adjacent questions. An agent must infer routing from the parameter shape alone.

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