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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds real value beyond them: server-side computation, no full-body transfer, and truncation reporting tied to max_lines. It doesn't cover failure modes (invalid revision IDs, posts with no revisions), which keeps it below a 5.

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?

Front-loaded with the core purpose, then defaults, then parameters, then output cap — a logical order with little waste. Minor redundancy in the trailing "Read-only" and "Through Royally: read-only, runs straight away" (the latter likely appended boilerplate) trims it from a 5.

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?

No output schema exists, and the description compensates by naming the output as a unified diff that is server-computed and truncated when capped. For a 5-param read tool with 1 required parameter this is nearly complete; only edge-case behavior (missing revisions, invalid IDs) is absent.

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 coverage is 80% and the schema already documents the from_revision_id/to_revision_id defaults and the max_lines cap, so the description mostly restates those semantics. With the schema doing the heavy lifting, baseline 3 is appropriate; the description adds the behavioral framing of defaults but no new syntax detail.

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 combination ("unified diff between two states of a post, computed server-side") and clarifies the default comparison (latest revision vs. live content). An agent can distinguish this from a revision-content fetch without opening any schema, since the description emphasizes diffing rather than transferring full bodies.

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?

Gives a clear primary use case ("what did my last write actually change?") plus an explicit secondary mode (pass from_revision_id / to_revision_id to compare any two revisions). It does not explicitly name sibling alternatives like wp_get_revision_content or wp_restore_revision and when to prefer them, so it stops short of a 5.

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