Read file contents: returns full content for files under 200 lines, outline for longer files, and supports optional line ranges.
Smart reader. <200L: full content. >200L: outline. Optional line range.
| Name | Required | Description | Default |
|---|---|---|---|
| file | No | Relative path to file (also accepts file_path) | |
| end_line | No | End line | |
| file_path | No | Alias for file | |
| start_line | No | Start line |
Changes observed during successful MCP inspections.
v1.10.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden and it does reveal the key adaptive threshold of 200 lines, which is genuinely useful. However, it does not disclose what an outline contains, how errors are handled, whether reads are read-only beyond the 'reader' framing, or any limits on the line range.
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 entire description is one front-loaded label plus three short clauses, with no filler. It is tightly structured so an agent can scan the threshold and optional-range behavior immediately.
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 simple read tool with no annotations and no output schema, the description covers the core usage and adaptive behavior, which is a minimum viable definition. It leaves gaps around the outline format, line-range inclusivity, and sibling selection, so it is not complete enough for nuanced choices.
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 input schema already documents all four parameters with 100% coverage, so the baseline is 3; the description adds that the line range is optional and relates it to the content/outline threshold. This is helpful but does not substantially deepen the meaning of start_line and end_line beyond what the schema already provides.
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 identifies this as a smart reader for files and specifies the adaptive behavior (<200 lines returns full content, >200 lines returns an outline) and optional line-range support. It is distinct from the generic name, but it does not explicitly distinguish itself from the read_file_outline sibling, and 'outline' is left undefined.
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 description implies when to use the tool: for reading a file, with an optional line range to narrow the read, and describes automatic behavior by file size. It does not, however, state when to choose read_file over read_file_outline or search_in_file, despite several closely related siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.