Send text input to an active REPL session, appending a newline by default to execute the command. Use it to automate code execution by submitting strings directly.
Write text to a REPL session. Appends a newline by default.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | ||
| text | Yes | ||
| newline | No |
Changes observed during successful MCP inspections.
v4.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries full burden. It discloses the newline default behavior, but omits important traits like whether input is echoed, session readiness requirements, or error handling. The single behavioral detail is insufficient for a mutation tool with no other sources.
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 sentences with zero waste. The first sentence front-loads the purpose, the second adds a critical default behavior. Every word earns its place.
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?
Given no annotations, no output schema, and 3 parameters, the description should provide more context (e.g., how to obtain session id, what happens after writing, error cases). It covers only the basic action and one default, leaving significant gaps for a reliable agent invocation.
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?
With 0% schema description coverage, the description must explain all parameters. It adds meaning for 'text' and 'newline', but entirely omits 'id' (the session identifier), which is required. This gap leaves the agent unable to understand which session receives the text.
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 verb 'Write' and resource 'text to a REPL session', making the tool's function specific and unambiguous. This contrasts with sibling tools like repl_key or repl_expect, which handle different REPL interactions.
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 provides no explicit guidance on when to use this tool versus alternatives (e.g., repl_key for key presses, repl_expect for pattern matching). It only implies use for sending text, but lacks exclusions or contextual boundaries.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.