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tmux_split_window

Split tmux terminal windows horizontally or vertically to create new panes for parallel command execution and terminal automation.

Instructions

Split the current window in a tmux session horizontally or vertically to create a new pane.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
session_nameYesName of the tmux session
verticalNoIf true, split vertically (side by side). If false, split horizontally (top and bottom). Default: false

Implementation Reference

  • Handler function that splits the tmux window horizontally or vertically based on the vertical parameter using tmux split-window command.
    async splitWindow(args) {
      const { session_name, vertical = false } = args;
    
      try {
        let cmd = `tmux split-window -t "${session_name}"`;
    
        if (vertical) {
          cmd += " -h"; // horizontal split creates vertical panes (side by side)
        }
    
        await execAsync(cmd);
    
        return {
          content: [
            {
              type: "text",
              text: `Split window in session ${session_name} (${
                vertical ? "vertically" : "horizontally"
              })`,
            },
          ],
        };
      } catch (error) {
        throw new Error(`Failed to split window: ${error.message}`);
      }
    }
  • Input schema defining parameters for the tmux_split_window tool: session_name (required string), vertical (optional boolean).
    inputSchema: {
      type: "object",
      properties: {
        session_name: {
          type: "string",
          description: "Name of the tmux session",
        },
        vertical: {
          type: "boolean",
          description:
            "If true, split vertically (side by side). If false, split horizontally (top and bottom). Default: false",
        },
      },
      required: ["session_name"],
    },
  • src/index.js:129-148 (registration)
    Tool registration in the ListTools response, including name, description, and input schema.
    {
      name: "tmux_split_window",
      description:
        "Split the current window in a tmux session horizontally or vertically to create a new pane.",
      inputSchema: {
        type: "object",
        properties: {
          session_name: {
            type: "string",
            description: "Name of the tmux session",
          },
          vertical: {
            type: "boolean",
            description:
              "If true, split vertically (side by side). If false, split horizontally (top and bottom). Default: false",
          },
        },
        required: ["session_name"],
      },
    },
  • src/index.js:201-202 (registration)
    Dispatch case in the CallToolRequestHandler switch statement that routes to the splitWindow handler.
    case "tmux_split_window":
      return await this.splitWindow(args);
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden of behavioral disclosure. It describes the action and outcome but lacks details on permissions needed, whether the split is reversible, how it affects existing panes, or error conditions (e.g., if the session doesn't exist). For a mutation tool with zero annotation coverage, this is insufficient.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, well-structured sentence that efficiently conveys the tool's purpose, action, and outcome without unnecessary words. It is front-loaded with the core action ('split the current window') and every element earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (mutation with 2 parameters), no annotations, and no output schema, the description is minimally adequate. It covers the basic action but lacks details on behavioral traits, error handling, or output format, which would be needed for full completeness in this context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both parameters ('session_name' and 'vertical') with clear descriptions. The description adds no additional meaning beyond what the schema provides, such as explaining parameter interactions or default behavior. Baseline 3 is appropriate when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('split the current window') and resource ('in a tmux session'), including the outcome ('to create a new pane') and the orientation options ('horizontally or vertically'). It distinguishes this tool from siblings like 'tmux_create_session' (creates sessions) and 'tmux_select_pane' (selects existing panes).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when needing to create a new pane in a tmux session, but does not explicitly state when to use this tool versus alternatives (e.g., 'tmux_create_session' for new sessions or 'tmux_list_panes' to view existing ones). It provides basic context but lacks explicit guidance on exclusions or prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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