Look up a system call

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

With no annotations provided, the description carries the full burden. It discloses the return behavior ('Returns its number, name, and any notes') and implies a read-only operation via 'Look up.' While it doesn't explicitly say 'does not modify anything,' the verb and return-value statement are sufficient for a simple lookup. It does not mention error handling or edge cases, but these are not critical for this level of transparency.

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 a single, well-structured sentence that starts with the verb, gives examples, and states what is returned. Every part is necessary and informative, with no wasted words. This is exemplary conciseness.

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 simple one-parameter lookup tool with no output schema, the description fully covers the necessary context: what it does, how to invoke it (with examples), and what it returns. It also specifies the system call version (4.2BSD), which adds important scope. There is no missing critical information for the agent to select and invoke this tool correctly.

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?

The schema already fully describes the parameter (100% coverage), so the baseline is 3. The description adds value by providing concrete examples ('2' or 'fork') and clarifying that both numeric and named lookups are supported, which reinforces the schema's description. This enrichment justifies a score above baseline.

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 the tool's function: 'Look up a 4.2BSD system call by number or name.' It gives concrete examples and specifies the resource (system call) and the action (look up). This distinguishes it from sibling tools like list_syscalls, which lists all syscalls rather than retrieving one.

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 clearly indicates when to use this tool: when you have a specific system call number or name to look up. It doesn't explicitly mention alternatives like list_syscalls for enumeration, but the context is clear from the wording and examples. There are no exclusions provided, so it falls short of the explicit alternative guidance at score 5.

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