add_chapter

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

Annotations already establish the profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=true). The description adds a genuinely useful constraint beyond that: Vimeo rejects two chapters on the same second, a real failure mode not present in the schema or annotations. 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?

Two sentences with zero waste. The action is front-loaded in the first sentence, and the second carries only the critical constraint needed to call the tool successfully.

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 three-parameter create operation, the essentials are covered: purpose, required parameters, and the key API constraint. The only gap is the response shape — specifically the created chapter's ID needed for later update/delete — which matters because there is no output schema.

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 description coverage is 100%, so all three parameters (video_id, timecode_seconds, title) already carry meaningful descriptions. The tool description reinforces the timecode concept but adds no per-parameter detail beyond the schema, warranting the baseline 3.

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 states a specific verb and resource: "Add a chapter marker at a timecode." This clearly identifies the operation and distinguishes it from sibling tools like list_chapters, update_chapter, and delete_chapter without ambiguity.

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 provides concrete operational context, notably the transcript-generation scenario and the requirement that timecodes be distinct to avoid Vimeo's duplicate-second rejection. It does not explicitly route to alternatives such as update_chapter for modifying existing chapters, so it stops short of a 5.

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