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* fix(tools): sandbox FileWriterTool writes and fix file tool rough edges FileReadTool confined reads to the working directory, but FileWriterTool only checked that `filename` stayed inside `directory` — and `directory` itself is an LLM-supplied schema field. An agent could therefore write anywhere the process had permission to, including ~/.ssh and site-packages, while the reader refused to read back what the writer had just written. FileWriterTool was the only filesystem tool in the package that did not go through validate_file_path; files_compressor_tool validates even its output path. Writes are now confined to base_dir (the working directory by default): the resolved directory must sit inside base_dir, and the resolved file must sit inside that directory. The pre-existing filename containment check is kept as-is and still applies even when the unsafe-paths escape hatch is on, so no existing guarantee is weakened. Both tools gain a base_dir field so a developer can widen the sandbox deliberately instead of reaching for the process-wide CREWAI_TOOLS_ALLOW_UNSAFE_PATHS kill switch. FileReadTool also stops rejecting a file_path given to its own constructor: that is developer-declared intent, and declaring one file does not expose its siblings. Also fixed: - FileReadTool scanned the whole file when reading a line window; it now stops via islice once the requested lines are collected. - FileWriterTool._run(**kwargs) made the documented positional call signature raise TypeError and turned a missing overwrite into "error accessing key". It now takes named parameters in the documented (filename, content, directory) order. - A directory naming an existing file reported "already exists and overwrite option was not passed" even with overwrite=True; it now explains the real problem. - Subdirectories inside filename are created, matching what passing directory already did. - Both tools now write and decode UTF-8 by default instead of the platform locale encoding, with an encoding field to override. The docs already claimed UTF-8 and recommended the writer to Windows users. - The writer's schema fields had no descriptions for the LLM. - Docs claimed FileReadTool parses JSON into a dict (it never has), shipped a snippet that raised TypeError, and did not mention the path sandbox. The writer README also began with a stray "Here's the rewritten README" preamble. BREAKING CHANGE: FileWriterTool no longer writes outside the working directory. Pass base_dir to authorize a different tree. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> * chore: update tool specifications * fix(tools): make the declared FileReadTool file reachable by agents Addresses review feedback on #6692. The constructor-path exemption did not actually work the way an agent calls the tool. The description only advertises a redacted label (the basename, when the file sits outside the sandbox), but resolution required the exact absolute path, so the model's call was sandboxed and the declared file was never read. Worse, file_path was a required schema field, so the long-documented "call with no arguments to read the default file" raised a validation error instead: FileReadTool(file_path="/outside/declared.txt") .run() -> ValueError: validation failed .run(file_path="declared.txt") -> Error: File not found .run(file_path="/outside/declared.txt") -> works, but the model was never told this path file_path is now optional in the schema, so omitting it reads the default, and the declared file is addressable by the label the description shows the model as well as by its real path. Declaring one file still does not expose its siblings. The declared path is also pinned to its real path at construction, so a later chdir cannot silently repoint it at a different file — previously a relative constructor path re-resolved against the new working directory on every call. Also guards the writer's filepath resolution, which could raise ValueError out of _run for a filename containing a null byte, breaking the contract of always returning a descriptive string. The directory and read paths were already guarded. Adds docstrings to strtobool and both _run methods, corrects an Arabic tanween spelling and a kaf-as-descriptor calque in the localized read docs, and regenerates tool.specs.json for the schema change. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> * fix(tools): anchor the declared read path to base_dir, not the cwd Addresses the second round of review feedback on #6692. The previous commit pinned a relative constructor file_path with os.path.realpath, which anchors to the working directory, while both format_path_for_display and validate_file_path anchor a relative path to base_dir. With the two roots disagreeing, the same relative string meant two different files — and the tool served the cwd one under a label that looks like it belongs to the sandbox: FileReadTool(file_path="data.txt", base_dir="/allowed") # cwd=/work label advertised to the model -> "data.txt" run(file_path="data.txt") -> contents of /work/data.txt That reads a file from outside base_dir, so it was a sandbox escape introduced by the exemption itself, not just a wrong-file bug. Resolution now goes through a single _resolve_against_base helper that anchors relative paths exactly the way the sandbox does, so the pinned path, the advertised label and the containment check all agree. Covered by test_relative_declared_path_anchors_to_base_dir. Also softens "always readable" to "always allowed past the containment check" in the docstring, README and docs, since bypassing containment does not guarantee the read succeeds — it can still fail on a missing file, a directory, or permissions. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> * fix(tools): tell the LLM about the path sandbox in tool descriptions Addresses the low-confidence notes from the Copilot review on #6692. Both tools' descriptions were pre-sandbox wording, so the model learned about containment only by attempting a path and reading the error back. Both now state that access is confined to the tool's allowed directory and that a path resolving outside it is rejected. The wording deliberately says "the tool's allowed directory" rather than "the working directory", because the root is base_dir when one is set, and naming the absolute root would leak it into the prompt — the same reason paths are redacted in errors. Not changed: the notes also suggested advertising `encoding`. That is a constructor-only field the model cannot set, so describing it to the LLM would be misleading. Also fixes a test docstring that contradicted its own assertion — the public run() path does raise on schema validation failure, which is what the test asserts. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> * fix(tools): anchor base_dir at construction so the sandbox cannot move Addresses the third review round on #6692. Both remaining findings came from the same habit: storing an unanchored string and re-resolving it later. A relative base_dir was kept verbatim and re-resolved against getcwd() on every call, while the declared file was pinned once at construction. After a chdir the sandbox root moved but the declared default did not, so one tool applied two different roots. base_dir is now resolved once — in the reader's __init__, and via a field_validator on the writer so it also applies on the model_validate path. That also covers the serialization concern. model_dump drops the private pin, and __init__ re-runs on restore, so a relative file_path was re-anchored against whatever the working directory happened to be at load time. With base_dir anchored, restore rebuilds the identical pin. The residual case is a relative file_path with no base_dir, where the sandbox root is the working directory too — so both move together and the tool stays self-consistent. Covered by test_declared_path_survives_a_serialization_round_trip and test_relative_base_dir_is_anchored_at_construction on both tools. Also corrects the writer's 'directory' description, README and docs: the default resolves inside the tool's allowed directory, which is base_dir when one is set, not always the working directory. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
82 lines
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82 lines
3.8 KiB
Plaintext
---
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title: File Write
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description: The `FileWriterTool` is designed to write content to files.
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icon: file-pen
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mode: "wide"
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---
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# `FileWriterTool`
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## Description
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The `FileWriterTool` is a component of the crewai_tools package, designed to simplify the process of writing content to files with cross-platform compatibility (Windows, Linux, macOS).
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It is particularly useful in scenarios such as generating reports, saving logs, creating configuration files, and more.
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This tool handles path differences across operating systems, writes UTF-8 by default rather than the platform's locale encoding, and automatically creates directories if they don't exist, making it easier to organize your output reliably across different platforms.
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## Installation
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Install the crewai_tools package to use the `FileWriterTool` in your projects:
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```shell
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pip install 'crewai[tools]'
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```
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## Example
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To get started with the `FileWriterTool`:
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```python Code
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from crewai_tools import FileWriterTool
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# Initialize the tool
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file_writer_tool = FileWriterTool()
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# Write content to a file in a specified directory
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result = file_writer_tool.run(
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filename='example.txt',
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content='This is a test content.',
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directory='test_directory',
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)
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print(result)
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```
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## Arguments
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The agent supplies these at runtime:
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- `filename`: The name of the file to write, relative to `directory`. May include subdirectories, which are created if they don't exist.
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- `content`: The text content to write into the file.
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- `directory` (optional): The path to the directory where the file will be created. A relative path resolves inside the tool's allowed directory — `base_dir` when set, the current working directory otherwise — and defaults to its root. If the directory does not exist, it will be created.
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- `overwrite` (optional): Whether to replace the file when it already exists. Accepts `true`/`false` (also `yes`/`no`, `on`/`off`, `1`/`0`). Defaults to `false`, which reports an error instead of replacing existing content.
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You set these when constructing the tool:
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- `base_dir` (optional): The directory that writes must stay inside. Defaults to the current working directory.
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- `encoding` (optional): Text encoding used to write the file. Defaults to `utf-8`.
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## Allowed paths
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Because both the directory and the filename are usually chosen by an LLM at runtime, writes are confined to a sandbox:
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- The resolved `directory` must be inside `base_dir`, which defaults to the current working directory.
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- The resolved file must then be inside that `directory`. `..` segments, absolute paths, and symlinks are resolved before both checks, so they cannot be used to escape.
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To let an agent write outside the working directory, point `base_dir` at the target tree:
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```python Code
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# The agent may write anywhere under /var/output, and nowhere outside it
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file_writer_tool = FileWriterTool(base_dir='/var/output')
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```
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<Note>
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Previously an absolute `directory` could write anywhere the process had permission to. If you relied on that, set `base_dir` to the tree you want to allow. Setting `CREWAI_TOOLS_ALLOW_UNSAFE_PATHS=true` restores the old behavior, but it applies process-wide to every crewai-tools tool, including the SSRF protections on URL-fetching tools, so prefer `base_dir`.
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</Note>
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## Conclusion
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By integrating the `FileWriterTool` into your crews, the agents can reliably write content to files across different operating systems.
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This tool is essential for tasks that require saving output data, creating structured file systems, and handling cross-platform file operations.
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It's particularly recommended for Windows users who may encounter file writing issues with standard Python file operations.
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By adhering to the setup and usage guidelines provided, incorporating this tool into projects is straightforward and ensures consistent file writing behavior across all platforms.
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