tac

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

Annotations already declare readOnlyHint=true, so the description's mention of 'Read-only, no side effects' reinforces that. But the description adds important behavioral details: returns JSON by default, and the --raw flag produces plain text output. There is no contradiction with 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?

Extremely concise: three short sentences covering purpose, behavior, alternatives, and related tools. No redundant or unnecessary text. Well-structured with front-loaded purpose.

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?

Despite having no output schema, the description clearly states the return format (JSON by default, plain with --raw). It covers the primary use case and behavior. With schema covering all parameters and no required fields, the description is fully adequate for an agent to understand and use the tool.

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 only briefly references '--raw' in passing but does not add new semantic meaning beyond what the schema already provides. Baseline 3 is appropriate.

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?

Clearly states the verb (reverse) and resource (order of input lines). Distinguishes from sibling tools 'sort' and 'cat' by explicitly noting that for reverse-sorted order one should use 'sort --reverse', not 'tac'. Also mentions it is read-only and without side effects.

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?

Provides explicit guidance on when to use the tool ('invert line order for LIFO processing') and when not to use it ('Not for sorting — use 'sort --reverse''). Directly names the alternative tool and command. Also references related tools 'sort' and 'cat' for further context.

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