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

Annotations already declare destructiveHint=true, readOnlyHint=false, and non-idempotent, so the safety profile is largely covered. The description adds genuinely new behavioral context: the operation is treated as sensitive and is gated behind an explicit confirm=true, which the agent must know to call it successfully.

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?

Two compact sentences with the core action front-loaded and the constraints immediately after. Nothing is padded, though the endpoint path is arguably redundant detail.

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 15-parameter destructive mutation with no output schema and thin schema coverage, the description covers the action and the confirm gate but omits which fields are updatable, auth requirements, and what changes are applied. It is adequate but leaves clear gaps.

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 only 40% across 15 parameters, so the description is expected to compensate, but it explains no field semantics (amount, spent_date, category_id, auth fields, etc.) beyond repeating the confirm requirement already documented in the schema. It leaves most parameters undocumented in both places.

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 verb and resource ('Updates an expense') and even cites the backing endpoint. It does not explicitly differentiate itself from siblings like create_expense, delete_expense, or update_events_batch, but the verb+resource pairing is unambiguous.

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 states a prerequisite ('requires confirm=true') and flags the operation as sensitive, which tells the agent a guard exists. However, it gives no guidance on when to prefer this single-record update over sibling alternatives such as batch update tools, nor any exclusions.

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