mkfifo

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

Annotations already set destructiveHint=true. The description adds behavioral context: 'creates a special file that blocks readers until a writer connects (and vice versa). Fails safely if the path already exists (idempotent).' This goes beyond annotations, though it does not contradict them.

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 description is informative and well-structured, starting with the main purpose. Every sentence adds value, but it is slightly lengthy. However, it remains organized and front-loaded with key information.

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 tool with 4 parameters, no output schema, and the given annotations, the description covers return format (JSON with path, mode, status), error handling (structured JSON with exit code and stderr), blocking behavior, idempotency, and safe failure. This is complete and actionable.

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 descriptions for all 4 parameters. The description adds value by noting 'Use --dry_run to preview without touching the filesystem,' 'Use --mode to set permissions (default 666),' and 'Use --parents to auto-create missing parent directories.' This enriches the schema information.

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 'Create named pipes (FIFOs) for inter-process communication,' specifying the verb and resource. It distinguishes from sibling tools by listing what it is not for (regular files, directories, device nodes) and naming alternatives (touch, mkdir, mknod).

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 explicitly says 'Use when you need a FIFO pipe' and provides exclusions: 'Not for creating regular files — use 'touch'. Not for regular directories — use 'mkdir'. Not for device nodes — use 'mknod'. See also...' This offers clear context and alternative tools.

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