update_transaction

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

The description adds a behavioral constraint beyond the idempotentHint annotation: the restriction on split/grouped transactions, and the v2 API envelope change which is important for agents that may have learned the older wrapper format. It doesn't contradict the annotation and adds meaningful context, though it doesn't describe side effects like balance updates (though update_balance is in 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?

Two sentences with zero waste. The core purpose is front-loaded, the envelope change is stated in a parenthetical, and the restriction/alternative is given in the second sentence. Every word earns its place.

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?

Despite being a complex tool with a nested update object and three parameters, the description covers the essential usage (how to update, what not to touch) and routes to alternatives. The schema already details all parameter constraints and mutual exclusions, so nothing an agent needs to call correctly is missing.

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% and all parameters have inline descriptions, so the schema carries the burden. The description's note about 'any subset of writable fields directly' adds a slight semantic hint about the update object structure but doesn't go beyond what the schema already implies. This is the baseline 3 for full schema coverage.

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 verb and resource ('Update an existing transaction') and immediately clarifies scope: it cannot modify split or grouped transactions, which distinguishes it from sibling tools like split_transaction or create_transactions. The purpose is unambiguous and unique among the many transaction-related 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?

Explicitly says when NOT to use it ('Cannot modify split or grouped transactions') and names the alternative ('use the corresponding split/group tools instead'). Also instructs how to provide fields ('any subset of writable fields directly'), giving clear usage context without needing to infer.

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