fs_write_chunkWrite UTF-8 or base64 data to a file by rewriting, appending, or writing at an absolute byte offset, enabling large files to be written in chunks.
Write UTF-8 or base64 data by rewrite, append, or absolute byte offset. Chunked calls remove any practical whole-file size limit.
| Name | Required | Description | Default |
|---|---|---|---|
| file | Yes | ||
| mode | No | append | |
| offset | No | ||
| content | Yes | ||
| deviceId | No | ||
| encoding | No | utf8 | |
| deviceName | No |
Changes observed during successful MCP inspections.
v0.8.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description adds the encoding options and the chunking/size claim, but does not state key behavioral details such as whether 'rewrite' truncates existing content, whether 'at' requires a valid offset, or whether a missing file is created.
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 dense sentences with no filler, and the write modes are front-loaded. It is appropriately sized, though slightly terse given the number of parameters it could have clarified.
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 7-parameter mutation tool with 0% schema coverage and no output schema, the description covers the core write concept and the chunking rationale but omits device targeting, the offset requirement for 'at' mode, and truncation behavior on rewrite. Adequate but with clear gaps.
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 does explain the semantics behind the 'mode' enum (rewrite/append/at byte offset) and the 'encoding' enum (UTF-8 vs base64), but leaves file, content, offset constraints, deviceId, and deviceName undocumented, covering only part of the 7 parameters.
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?
The description states a specific verb (Write) and resource (file chunk) and enumerates the three write modes (rewrite, append, absolute byte offset), so an agent knows what the tool does. It does not, however, differentiate from close siblings like fs_write_text, fs_write_many, or edit_block.
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?
Usage is only implied: 'Chunked calls remove any practical whole-file size limit' hints that this tool is for large writes that need chunking, but it never names fs_write_text or fs_write_many as alternatives nor states when a single whole-file write is preferable. No explicit when/when-not guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.