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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely non-obvious domain semantics: amounts are integers in minor units (45000 = 450.00) and dates/months use family-time-zone conventions, which an agent needs to interpret what comes back. It does not cover behavior for a missing or invalid id.

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 short, front-loaded sentences with no filler; the retrieval clause comes first and the format conventions follow. Slightly odd that most of the text is about return-value formatting rather than the operation itself.

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 is the only place return information can live, and it explains value units and date formats but never describes the entry's fields, structure, or what happens when the id is not found. Partial compensation for the missing output schema.

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 0% for the single required `id` parameter, but the parameter is self-describing (a string id) and the description only restates that the lookup is "by its id". No format hints are added beyond what the schema name/type already convey.

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?

"One entry by its id" implies a single-record fetch, but the resource is called an "entry" rather than a transaction and no retrieval verb is used, so the reader has to infer the operation from the sibling list. It distinguishes single-fetch from list_transactions only weakly, and leans on the title ("One entry") for meaning.

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?

There is no guidance about when to use this tool versus list_transactions, get_analytics, or any other read sibling, and no mention of prerequisites or failure conditions. Only the implicit "by its id" signals single-record retrieval.

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