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sassy_diff

Read-onlyIdempotent

Compare two files to see exactly what changed, including added and removed lines, with a unified diff. Returns identical status and counts to confirm differences before copying or restoring.

Instructions

Read-only. Compares two files and returns a unified diff. Both files are read as UTF-8 (decoding errors replaced); returns an error if either path does not exist. context_lines (integer, default 3) sets how many unchanged lines surround each hunk. The response includes identical (true when files match), lines_added and lines_removed counts, and diff text truncated at 20,000 characters. It compares file contents only, not metadata like timestamps or permissions. Use it to verify exactly what changed between two file versions before copying, restoring, or reviewing them.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`path_a`	Yes
`path_b`	Yes
`context_lines`	No

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv1.15.1Sep 18, 2026

addedOutput schema / additionalProperties
```
Added value: +true
```

removedOutput schema / properties

Removed value: -{
-  "result": {
-    "title": "Result",
-    "type": "string"
-  }
-}

removedOutput schema / required
```
Removed value: -[
-  "result"
-]
```

changedOutput schema / title

Previous value: -"sassy_diffOutput"New value: +"sassy_diffDictOutput"

First observedv0.1.0Jul 31, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description discloses substantial behavior: UTF-8 decoding with replacement, error behavior for missing paths, default and effect of context_lines, response fields (identical, lines_added, lines_removed, truncated diff text), and the fact that metadata is ignored. This goes well beyond what the annotations alone provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured and front-loaded: read-only status and core action first, then encoding, errors, parameters, output, scope, and use case. Each sentence adds distinct information without redundancy, making it efficient for an agent to parse and act on.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with an output schema and strong annotations, the description covers all essential operational aspects: inputs, defaults, error cases, output contents and truncation limit, scope limitations, and a recommended use case. An agent has everything it needs to select and invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must carry the parameter documentation burden. It clearly explains context_lines ('sets how many unchanged lines surround each hunk') and its default of 3. path_a and path_b are referred to as 'two files' and the encoding/error behavior adds useful meaning, though the description could more explicitly define their roles as source and target for diff direction.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with 'Compares two files and returns a unified diff,' a specific verb and resource that clearly identifies the tool's function. It further distinguishes itself from siblings like read_file or file_info by emphasizing content-only comparison and diff output, leaving no ambiguity about its purpose.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description states a concrete use case: 'Use it to verify exactly what changed between two file versions before copying, restoring, or reviewing them.' It also clarifies that it compares file contents only and not metadata, which implicitly steers agents away from using it for metadata checks. However, it does not explicitly name alternative tools or state when not to use it, so the guidance is clear but not fully exhaustive.

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

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