label_add_at

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

With no annotations, the description carries the behavioral disclosure burden. It explicitly discloses the side effect 'Changes the current selection as a side effect' and the composed mechanism select_region + label_add, which is valuable transparency. It does not mention return values or error behavior, but for a simple add operation this is a strong disclosure.

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 compact, front-loaded with the core purpose, and uses a short Args block for parameters. The source-comment reference is slightly extra but supports credibility rather than padding.

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 label-adding tool with no output schema, the description covers the essential behavior, the selection side effect, and all parameter semantics. It could be more complete by mentioning what the operation returns or whether it is undoable, but it provides enough context for correct invocation.

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 0%, and the description compensates by documenting all three parameters with meaningful details: start/end are in seconds, end must be >= start, and text is optional. This adds real semantic value beyond the bare input schema, though it stays fairly minimal.

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 'Add a label at an exact time range, regardless of the current selection,' which precisely identifies the verb, resource, and distinctive behavior. It distinguishes itself from sibling label_add by explicitly noting that it does not depend on the current selection and explains its composition from select_region + label_add.

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 implies when to use this tool: whenever an exact start/end range is known and the current selection should not matter. It references label_add's selection-dependent behavior, giving useful context for choosing between the tools, though it does not explicitly state 'use label_add when you want the current selection' as an exclusion.

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