Send data to the stdin of an existing process started with process_start, enabling interaction with REPLs, prompts, and interactive CLIs. Set close to also close stdin.
Write text to stdin of a process started with process_start (REPLs, prompts, interactive CLIs). close: true writes the data and closes stdin.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | ||
| data | Yes | ||
| close | No |
Changes observed during successful MCP inspections.
v1.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true, readOnlyHint=false, and idempotentHint=false, so the agent knows this mutates a running process irreversibly. The description adds one genuinely useful behavioral detail beyond the annotations: close:true writes the data and closes stdin. It does not say what happens if the id is stale or the process has already exited.
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 tight sentences with zero filler. The core action is front-loaded and the close:true caveat follows immediately after.
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 three-parameter, no-output-schema tool, this covers the essential action and the one non-obvious parameter. The remaining gap is minimal: id and data are only implicit, and there is no note on error behavior for a dead process.
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 coverage is 0%, so the schema gives no help. The description explains the optional close parameter's effect well, and 'text to stdin' implies data while the process_start reference implies id, but neither id nor data is described explicitly, leaving the agent to infer their meaning.
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 states a specific verb+resource ('Write text to stdin of a process') and ties it to the sibling that creates the process (process_start), so the agent knows these two go together. It falls short of 5 because it never distinguishes itself from pty_write, which reads and writes to an interactive terminal and could easily be confused with this tool.
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?
It gives concrete usage context ('REPLs, prompts, interactive CLIs') and a prerequisite ('a process started with process_start'). It does not state any when-not condition or name an alternative tool, so it stops short of explicit routing.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.