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

With no annotations, the description carries the burden. It explains the three transformations clearly but does not disclose the return format (e.g., that it returns modified subtitle text) or any side effects. For a tool that likely modifies input content, this is a notable omission, but the core behavior is well-covered.

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, tightly packed sentence that front-loads the core purpose and then enumerates the three modes with examples. No wasted words, and the essential constraint is stated clearly.

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?

Given 5 parameters, full schema coverage, and no output schema, the description covers the main usage scenarios thoroughly. It does not address error handling when multiple modes are passed, but the explicit instruction to pass exactly one reduces ambiguity. Overall, a complete and useful definition for an agent to operate 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?

Schema coverage is 100%, so baseline is 3. The description adds significant value beyond the schema: the constraint to pass exactly one of the three, the example ratio value (1.0427 for 25→23.976), and the sign meaning for offset_seconds ('Negative = earlier'). This clarifies usage and relationships between parameters.

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 opens with a clear verb+resource ('Fix subtitle timing') and immediately distinguishes three specific adjustment modes (offset_seconds, ratio/fps). This clearly separates it from sibling tools like clean_subtitles or convert_subtitle, which handle different concerns.

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 each method: offset_seconds for uniform shift, ratio/fps for progressive drift, and mandates 'Pass exactly one of the three.' This directly guides selection among the three approaches and implies the alternatives.

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