update_expense

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

With no annotations, the description carries the burden of disclosing behavior. It usefully explains the partial-update semantics and preservation of omitted fields, which is the most important behavioral trait. However, it does not mention what happens when the id is invalid or not found, whether updates are irreversible, or any permission/error implications beyond what the schema implies.

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 sentences, no filler, and the core partial-update behavior is front-loaded. Every sentence contributes to correct usage.

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 tool with 6 parameters and an output schema, the description plus schema is largely sufficient to invoke the tool correctly. It covers the main behavioral nuance (partial update). It could be more complete by noting behavior for a nonexistent expense and whether passing only an id is a no-op, but these are gaps rather than blockers.

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 the schema already documents each parameter. The description adds meaningful cross-parameter semantic value by clarifying that omitted fields remain unchanged, which helps disambiguate the default-null pattern in the schema. This is a genuine contribution beyond the schema's per-field notes.

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 clearly identifies the verb (Update), the resource (an existing expense), and the key distinction that this is a partial update rather than a full replacement. This separates it cleanly from add_expense and delete_expense even without naming them.

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?

The description gives clear context: use this when updating an existing expense, and only the provided fields change. It does not explicitly name alternative tools or state exclusions like 'use add_expense to create a new expense,' but the existing-expense framing makes the primary use case unambiguous.

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