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

Annotations already cover read-only, idempotent, non-destructive semantics, and the description still adds real value beyond them: the result ordering (newest first), the fact that each entry carries its lines, and that the call is free (no billing cost). It stops short of noting pagination defaults or result-size limits.

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?

One dense sentence, front-loaded with the ordering and payload shape, with zero filler. It is slightly hard to scan as a run-on, and the trailing 'Free' feels appended rather than integrated, but no sentence is wasted.

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 an optional-parameter list tool with no output schema, the description covers the essentials: what is returned (entries with lines), ordering, and the main filter axes. The gaps are the pagination and entry-number parameters and the truncated source enum, which the schema covers on its own.

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?

With 50% schema coverage, the description compensates partially: it explains that `text` searches memo, reference and party, and that the date and account filters exist. However, it never mentions `entry`, `limit` or `offset`, and its enumerated source list (7 values) is a subset of the 17-value schema enum, so an agent relying on the prose would under-use the filter.

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?

Names the resource (entries) and adds concrete distinguishing detail: newest-first ordering, each entry returned with its lines, and the available filters. An agent can tell this is a read/list tool for the books ledger, distinct from books_get or books_report, though the verb is elided rather than stated.

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 only implied by describing the filters (dates, account, source, text); there is no explicit 'use this when...' statement, no mention of when to prefer books_get for a single entry or books_report for aggregates, and no prerequisite guidance. The filter list does help an agent infer the retrieval use case.

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