Transactions: get transaction by id_by_customer

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context: it is READ-ONLY, makes no changes to accounting records, and returns an array of transaction data. It also clarifies the semantics of id_by_customer, which is a meaningful behavioral detail beyond the schema. No contradiction with annotations.

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 reasonably concise but contains redundancy: the title and the bolded line both say 'get transaction by id_by_customer', and the endpoint line is repeated in the description. The READ-ONLY note is useful and front-loaded, but the middle section could be tightened. It is not as crisp as it could be.

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?

Given the tool has zero parameters, an output schema, and strong annotations, the description covers the essential context: what it does, how to get the id, and when to use the sibling list tool. It does not describe the output structure, but the output schema exists, so that is not required. The only minor gap is not explaining why the endpoint is POST /transactions/get/id_by_customer, but that is not critical for invocation.

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 input schema has zero parameters, so the description cannot add parameter-level detail. The description does explain the key concept id_by_customer and how to obtain it, which is the closest thing to parameter semantics here. With 0 params, the baseline is 4, and the description earns it by explaining the lookup key's meaning and source.

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 states a specific verb and resource: fetch a single bank transaction by id_by_customer. It also clarifies that id_by_customer is a per-customer counter, not a global database id, which helps distinguish the lookup key. However, the title and description contain redundant phrasing ('get transaction by id_by_customer') and the endpoint line is somewhat confusing, so it is not a perfect 5.

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 to use transactions_list for searching or paging through transactions, and says to use this tool when you already have the id. It also tells the user how to obtain id_by_customer via the /transactions/get method first. This is clear usage guidance, though it does not enumerate all alternatives or explicitly say when not to use it beyond the list/search case.

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