Append text to the end of a file, creating it if missing, to update logs, configs, or notes without overwriting existing content.
Appends text to the end of an existing file (or creates it if it doesn't exist).
| Name | Required | Description | Default |
|---|---|---|---|
| source | No | ||
| content | Yes | ||
| file_path | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the burden of explaining side effects. It accurately discloses the core behavior — appending to an existing file or creating it if absent. It does not mention permission requirements, encoding, or newline handling, but these are minor for such a simple operation.
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?
The description is a single, compact sentence with no filler. It efficiently conveys the essential operation and the create-if-missing fallback.
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 the primary action but leaves crucial context out: the 'source' parameter is not addressed, and no mention is made of the output or return value. Since the tool operates on files and has an output schema, a complete description should clarify these aspects.
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?
The description names 'text' and 'file' informally, but it does not explicitly explain the three parameters. In particular, 'source' is completely unexplained — its role is unclear (e.g., whether it's a source file, a session reference, or something else). Since schema coverage is 0%, the description fails to compensate for the lack of parameter documentation.
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 clearly states the tool's action: appending text to a file, with a explicit fallback to creating the file if it doesn't exist. The verb 'append' and resource 'file' make the purpose unambiguous, and it distinguishes naturally from siblings like write_file or edit_file by its specific behavior.
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 explicit guidance is given about when to use this tool versus alternatives. It doesn't state 'use this when you need to add to an existing file without overwriting' or contrast with write_file/edit_file. The behavior is implied but not directly advised.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.