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

With no annotations, the description carries the full burden and does substantial work: it discloses recursion into objects/arrays, that type changes are flagged as changes, deterministic behavior, and the x402 price/per-call cost. It omits behavior on invalid JSON input and ordering guarantees, keeping it from 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 capability and output format, then behavioral details, then usage and pricing. Mostly earns its place, though 'Deterministic, unlike eyeballing' partly restates the earlier structural-diff point.

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 describing the return content (added/removed/changed values with JSON Pointer paths). Combined with the two fully-described inputs, it is nearly complete, missing only error/edge-case handling.

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 100% (both a and b documented as 'before'/'after'), so the schema already handles parameter meaning. The description adds no syntax, format, or encoding detail beyond what the properties already provide, making the baseline 3 appropriate.

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 (compare) and resource (two JSON documents) with the distinctive output format (RFC 6901 JSON Pointer paths). The phrase 'not a text blob' and the contrast with text diffs cleanly separates it from siblings like dev_diff.

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?

Explicitly says to use it 'when an agent needs to structural diff with exact JSON Pointer paths', giving a clear use context and contrasting it with text diffs. It does not name dev_diff as the alternative or state when not to use it, so it stops short of a full when/when-not guide.

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