head

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

Adds 'Read-only, no side effects' which complements the annotations. Discloses behavior for negative-N and raw output, providing context beyond annotations.

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?

Three concise sentences with front-loaded purpose, then behaviors, then usage guidance. No wasted words.

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?

Covers purpose, behavior, parameter nuances, and usage context. Lacks detail on encoding parameter but is sufficient given the tool's simplicity.

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%, so baseline is 3. The description adds meaning for the 'lines' parameter (supports negative-N) and mentions raw output, improving clarity over the schema alone.

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 'Return the first N lines (default 10) of files or stdin as JSON', specifying the verb, resource, and output format. It also distinguishes from 'tail' by noting it's for viewing file beginnings.

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?

Explicitly states when to use ('preview file beginnings or extract headers'), when not to use ('Not for viewing file endings'), and provides alternatives ('use tail for the last N lines', 'See also tail, cat').

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