List Timeline Markers

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

The readOnlyHint annotation already covers the safety profile. The description adds behavioural detail about the enumeration (GetFirstMarker + GetNext) and the exact fields returned, plus the index handle. This is more than the annotation provides, though it doesn't discuss performance or edge cases. Since the tool is a simple list, this is sufficient.

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 two sentences, front-loaded with the core purpose and output details, then the usage guidance. Every sentence earns its place with no redundancy or fluff. It's concise and well-structured.

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 tool with no parameters, no output schema, and a read-only annotation, the description provides all necessary context: what it returns, the index handle for further operations, and when to use it. The agent can call this tool correctly without needing additional information.

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 tool has zero parameters, so the schema is empty and schema coverage is 100% by default. The description naturally adds nothing about parameters. As a baseline for no-parameter tools, this is appropriate; the description instead focuses on the output, which is the main semantic content.

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 purpose: to enumerate every timeline marker in the active document, listing specific fields (frame, time_seconds, name, colour, length_frames) and even notes the underlying API. It distinguishes itself from get_document_state by mentioning that get_document_state only reports marker_count, making it evident when this tool is appropriate.

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?

It explicitly states when to use this tool: 'Use this to verify marker placement' and contrasts it with get_document_state. This gives the agent a clear decision rule for selecting between sibling tools. The mention that the index handle is accepted by set_marker/remove_marker also informs downstream usage.

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