mkfifo

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

Describes destructive behavior: 'creates a special file that blocks readers until a writer connects (and vice versa).' Also mentions idempotency: 'Fails safely if the path already exists.' The annotation destructiveHint=true is supported and added context.

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?

Description is a single paragraph but concise (5 sentences) with most important info at the start. Could be slightly more structured (e.g., bullet points) but remains effective.

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?

No output schema provided, yet description explains return values: 'Returns JSON with the created path, mode, and status on success; on error, returns structured JSON with exit code and error message on stderr.' Covers both success and error scenarios.

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 100% with parameter descriptions. Description adds value by explaining use of each parameter: '--dry_run to preview without touching the filesystem', '--mode to set permissions (default 666)', '--parents to auto-create missing parent directories.'

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?

Description starts with 'Create named pipes (FIFOs) for inter-process communication', clearly stating the specific verb and resource. It distinguishes from siblings by explicitly saying 'Not for creating regular files — use touch', etc.

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?

States when to use: 'Use when you need a FIFO pipe for shell-style IPC between processes.' Also explicitly states when not to use with alternative tools: 'Not for creating regular files — use touch. Not for regular directories — use mkdir. Not for device nodes — use mknod.'

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