create_annotation

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

No annotations are provided, so the description carries full burden. It mentions the dry_run parameter for previewing without executing, which adds transparency. However, it does not disclose other behavioral traits such as permissions needed, whether mutations are reversible, or any side effects beyond creation. Adequate but could be more thorough.

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 efficient: a one-sentence purpose, a brief contextual note, and a clear arg list. Every sentence adds value with no fluff. It is front-loaded with the action and provides essential details in a structured format.

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 6 parameters (4 required), no annotations, and an output schema, the description explains each parameter and provides usage context. It does not describe the output, but since an output schema exists, that is acceptable. It could mention constraints like overlapping annotations or confirmation behavior, but overall it is fairly complete.

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 description includes a detailed Args section covering all 6 parameters, including formats (ISO 8601 for datetimes) and the meaning of dry_run. The input schema has 0% description coverage, so the description fully compensates and adds significant value beyond the raw schema.

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 'Add an annotation to an existing annotation layer.' This specifies the verb (add), resource (annotation), and scope (to an existing layer). It distinguishes from sibling tools like create_annotation_layer (which creates layers) and delete_annotation.

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 context by explaining annotations are time-based markers for time-series charts and advises to use list_annotation_layers or get_annotation_layer to find layer IDs. It implicitly suggests using this tool when you have an existing layer, but does not explicitly state when not to use it or list alternatives.

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