Replace a specific text fragment in a UTF-8 file after verifying SHA-256 hash. Rejects ambiguous or conflicting edits.
Replace exactly one literal fragment in a UTF-8 file after checking its SHA-256. Rejects ambiguity and conflicting edits.
| Name | Required | Description | Default |
|---|---|---|---|
| file | Yes | ||
| new_text | Yes | ||
| old_text | Yes | ||
| expected_sha256 | Yes |
Changes observed during successful MCP inspections.
v0.2.0-preview.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the destructiveHint=true annotation by disclosing the SHA-256 verification, rejection of ambiguity, and rejection of conflicting edits. This explains failure conditions and safety behavior that annotations alone do not provide.
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?
Two sentences, no filler. The core behavior is front-loaded, and the second sentence adds critical rejection conditions without 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?
The description covers invocation and rejection conditions well, but with no output schema it does not state what happens on success (return value, confirmation, or updated content). Also omits edge-case behavior like empty new_text or missing file, leaving some ambiguity for an agent.
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?
Despite 0% schema description coverage, the description compensates by clarifying semantic roles: old_text must be a unique literal fragment and expected_sha256 is verified before replacement. It does not explicitly map each parameter, but names plus schema patterns make the input understandable.
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 action ('Replace exactly one literal fragment'), a resource (UTF-8 file), and a key precondition (SHA-256 check). This clearly distinguishes it from siblings like write_file and read_file.
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 description conveys clear context—use this when you need to replace a single, unique literal fragment and verify content integrity first. However, it does not explicitly name alternatives (e.g., write_file) or state when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.