Replace an inclusive line range in a file with new text, or insert text before a line by setting the end line one less than the start.
Replace lines start_line..end_line (1-based, inclusive) with new_text. Use end_line=start_line-1 to insert before start_line.
| Name | Required | Description | Default |
|---|---|---|---|
| path | Yes | ||
| dry_run | No | ||
| end_line | Yes | ||
| new_text | Yes | ||
| start_line | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.2.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this is a mutation (readOnlyHint=false) that is neither idempotent nor destructive, and the description adds genuinely useful semantics: line numbering is 1-based and the range is inclusive. It does not say what happens on out-of-range line numbers, whether the file must exist, or what dry_run actually does, so behavioral coverage is partial rather than rich.
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 short sentences, front-loaded with the primary operation and followed immediately by the non-obvious insertion trick. No filler.
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?
A lean two-sentence definition that covers the core operation and its one non-obvious edge case, appropriate for a tool whose schema and annotations already carry the signature and safety profile; return behavior is covered by the output schema.
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 carries the burden and does explain start_line/end_line semantics and the insertion convention. However, dry_run (a boolean defaulting to false) is left completely unexplained, and path/new_text meanings are only implied, so the compensation is incomplete.
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+resource: replace a 1-based inclusive line range with new_text, which is precise enough to act on. It does not distinguish itself from close siblings such as edit_file, edit_file_multi, or create_file, so an agent must infer which mutation tool to pick.
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 only usage guidance is an edge case (end_line=start_line-1 inserts before start_line). There is no statement of when to prefer this over edit_file/edit_file_multi, nor prerequisites such as the file needing to exist or line numbers being in range.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.