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

readOnlyHint=true already covers the safety profile, and the description builds on that by disclosing the return envelope (JSON:API { data }) and, importantly, that the response contains PII, plus the underlying REST route. That PII warning is meaningful context an agent would not get from the annotation alone.

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?

Three tight clauses, front-loaded with the core action and free of filler. The trailing REST route restates the operation already evident from the name and schema, so it is mildly redundant but not wasteful.

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?

With no output schema, the description carries the return-value burden and does so — it names the envelope and flags PII. For a one-parameter read tool whose annotations already cover safety, nothing needed to call it 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 description coverage is 100% with a single required parameter documented with an example (txn_...), so the baseline is 3. The description adds only the REST path shape GET /transactions/{transaction_id}, which reinforces but does not meaningfully extend 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?

States a specific verb+resource ('Get a single transaction by id'), defines what a transaction is ('a record submitted for transaction fraud/monitoring analysis'), and the word 'single' plus 'by id' distinguishes it from the sibling persona_list_transactions. An agent can pick this over the other get_*/list_* siblings by resource alone.

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?

Usage is implied — retrieve one transaction when you have its id, versus listing many — but the description never names an alternative or an explicit when-not condition. It leaves the list-vs-get routing to inference rather than stating it.

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