Create, overwrite, or append UTF-8 files with atomic writes and optional SHA-256 checks. Use for safe file updates in automated workflows.
Create, overwrite or append a UTF-8 file. Overwrites are atomic by default and can use expectedSha256 as an optimistic concurrency guard.
| Name | Required | Description | Default |
|---|---|---|---|
| mode | No | overwrite | |
| path | Yes | ||
| atomic | No | ||
| content | Yes | ||
| createParents | No | ||
| expectedSha256 | No |
Changes observed during successful MCP inspections.
v0.2.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (readOnlyHint=false, destructiveHint=true, idempotentHint=false, openWorldHint=false). The description adds non-obvious behavioral context beyond that: atomicity is the default and expectedSha256 serves as an optimistic concurrency guard. That's genuinely useful. However, it omits what happens on concurrency conflict, whether append is atomic, or what atomic=false implies.
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, zero waste. The primary verbs and the default behavior are front-loaded, followed by the concurrency-guard detail. Every clause carries information.
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 6-parameter mutation tool with no annotations on atomic semantics and no output schema, the description supplies the critical missing context (atomic write, optimistic concurrency). It leaves append-mode behavior and conflict/error semantics unexplained, so it isn't fully complete.
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 0%, so the description must compensate. It explains the purpose of two non-obvious parameters: atomic (default overwrite atomicity) and expectedSha256 (optimistic concurrency guard). It does not cover mode semantics (overwrite vs append), createParents, or path/content, but the parameters it does address are the highest-value ones.
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 set (create, overwrite, append) and resource (UTF-8 file). It is distinguishable from fs_read and fs_patch by naming the write semantics, though it doesn't explicitly contrast with fs_patch, which also modifies files. Clear but no sibling differentiation.
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?
No guidance on when to use this tool versus fs_patch (for edits) or when to choose append vs overwrite mode. The description conveys capability but no selection criteria or conditions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.