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

The annotations provide basic safety hints (readOnlyHint=false, destructiveHint=false), indicating this is a write operation but not destructive. The description does not add further context about side effects, partial vs full updates, or error behavior. Since the bar is lowered by the presence of annotations, but the description itself adds no extra behavioral detail, a score of 3 is appropriate.

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 description is exceptionally concise, consisting of two sentences. It leads with the core action ('Update a transaction by id') and then immediately offers the alternative for bulk updates. There is no redundant information, making it well-structured and easy to parse.

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 simple update operation, the description is sufficiently complete. It states the primary action and the key alternative. It does not specify return values or error handling, but given the absence of an output schema and the straightforward nature of the tool, these omissions are minor. The context is adequate for an agent to understand the tool's role.

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?

The schema includes 11 parameters, all with descriptions, achieving 100% coverage. The tool description adds no extra meaning to these parameters beyond what the schema already provides. Given the high schema coverage, a baseline score of 3 is warranted.

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 states the tool's purpose: 'Update a transaction by id.' It is specific about the action and the resource, and it distinguishes the single-update tool from the bulk variant. This makes the purpose immediately obvious without needing to inspect the schema.

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 explicitly says when not to use this tool: 'To update several transactions at once, prefer update_transactions_bulk.' This provides clear guidance on choosing between the single and bulk operations. The distinction from other entity-specific update tools is implicit from the resource name, but the bulk alternative is explicitly called out.

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