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

Annotations cover the safety profile (readOnly, idempotent, closed-world), and the description adds real value beyond them by describing the return shape: a unified-style patch plus a per-line change list with added/removed/unchanged arrays. There is no output schema, so this disclosure matters. It loses a point because the two "Returns" sentences are slightly inconsistent about whether the output is a patch or categorized arrays.

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?

The purpose is front-loaded in the first sentence and the whole definition is three short lines with no filler. The duplicate "Returns" statements cost a point for slight redundancy.

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 a simple two-string, read-only tool with no output schema, the description supplies what an agent needs: the comparison granularity, the return structure, and a concrete example. Nothing critical is missing, though edge-case behavior on empty input or trailing newlines is unstated.

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%, so the baseline is 3. The example input does add modest value by showing that newlines are embedded literally in the JSON strings and that `a` is the original and `b` the modified text, but it repeats rather than extends the schema's descriptions.

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?

"Compute a line-level diff between two strings" gives a specific verb (compute a diff), resource (two strings), and granularity (line-level). That distinguishes it reasonably from siblings like hash_compare or list_compare, though it never names them explicitly.

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?

The "line-level" qualifier implies this is for line-oriented text comparison rather than value or byte comparison, which is useful implied guidance. However, there is no explicit when-to-use statement and no mention of alternatives such as list_compare for set-style comparison.

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