fast-filesystem-mcp

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fast_edit_blocks

Perform multiple precise text block replacements in a file in one operation. Each edit matches exact existing text, with optional expected replacement count and backup creation.

Instructions

Processes multiple precise block edits at once (array of fast_edit_block)

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "path": "<path>",
      "edits": "<edits>"
    },
    "name": "fast_edit_blocks"
  }
}

Input Schema

Name	Required	Description
`path`	Yes	Path of the file to edit
`edits`	Yes	List of precise block edits
`backup`	No	Create a backup

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedv1.0.0Jan 3, 2026

changedInput schema / properties / backup / description

Previous value: -"백업 생성"New value: +"Create a backup"

changedInput schema / properties / edits / description

Previous value: -"정교한 블록 편집 목록"New value: +"List of precise block edits"

changedInput schema / properties / edits / items / properties / expected_replacements / description
```
Previous value: -"예상 교체 횟수"New value: +"Expected number of replacements"
```
changedInput schema / properties / edits / items / properties / new_text / description
```
Previous value: -"새로운 텍스트"New value: +"The new text"
```

changedInput schema / properties / edits / items / properties / old_text / description

Previous value: -"정확히 매칭할 기존 텍스트"New value: +"The exact existing text to match"

changedInput schema / properties / path / description

Previous value: -"편집할 파일 경로"New value: +"Path of the file to edit"

First observedAug 22, 2025

TDQS

C2.9/5.0

Behavior2/5

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

No annotations exist, so the description must disclose behavior. It only mentions 'precise block edits' but omits atomicity, error handling, whether edits are applied sequentially or in parallel, and the effect of the backup parameter.

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

Conciseness4/5

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

Single sentence with no fluff, efficiently communicating the core purpose. However, it could be slightly more informative without losing conciseness.

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

Completeness2/5

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

Given the complexity of batch edits and lack of output schema, the description is insufficient. It should explain how edits are applied (e.g., order, atomicity) and differentiate from sibling batch edit tools.

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

Parameters3/5

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

Schema coverage is 100% with detailed descriptions for all parameters. The description adds no additional meaning beyond what the schema provides, so baseline 3 applies.

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

Purpose4/5

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

The description clearly states it processes multiple precise block edits at once, distinguishing it from single-edit siblings like fast_edit_block. However, it doesn't differentiate from fast_edit_multiple_blocks, which may be overlapping.

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus alternatives, such as fast_edit_block for single edits or fast_edit_multiple_blocks. No prerequisites or exclusions provided.

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