update_transaction

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

Annotations already establish that this is a mutating (readOnlyHint=false) but idempotent operation; the description adds a meaningful behavioral guarantee that unspecified fields are preserved. It does not cover return values or side effects on budgets/categories, but the partial-update disclosure goes beyond the structured metadata.

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 entire definition is a single 13-word sentence with the key behavior front-loaded. No filler or redundant restatement of the title.

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 7-parameter mutation with no output schema, the description plus schema covers the main call contract and the partial-update semantics. It leaves ambiguous what a successful update returns and when the sibling recategorize_transaction should be preferred, but those are secondary for making a correct call.

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?

All seven parameters have descriptions in the JSON schema, so the schema carries the semantic load. The description's 'only the fields you provide will be changed' reinforces optionality but does not add details about date formats, amounts, or categories beyond the schema.

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?

Uses a specific action verb ('Update') and a concrete resource ('existing transaction'), and the phrase 'fields you provide' signals a partial edit. It does not explicitly contrast with sibling recategorize_transaction, but it is clear enough about the general operation.

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 text implies use for modifying fields of an existing transaction and emphasizes that only supplied fields change, which orients an agent toward partial updates. It provides no explicit exclusions or mention of alternatives such as recategorize_transaction for category-only edits, so the guidance is mostly implicit.

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