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

Beyond the annotations, the description discloses important behavior: the widget initially shows demo data until pointed at an uploaded CSV dataset, and the returned widget_id is used for later updates. It also specifies that position, width, and height match the editor's Custom Data card. This meaningfully adds behavioral context beyond the readOnlyHint/destructiveHint flags.

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 three sentences with no filler. It front-loads the core purpose, then gives the return value and follow-up workflow, and finally the layout behavior. Every sentence contributes useful information.

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?

The description is complete for a tool with three well-documented parameters and an output schema. It specifies the return value, the relationship to update_custom_data_widget, and the source of IDs and column names. No critical information needed to understand or call the tool is missing.

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 input schema already covers all three parameters at 100% with clear descriptions, so the description does not need to repeat them. It adds contextual workflow information about the widget_id and update path, but not new meaning for the individual parameters. Per the calibration baseline, schema coverage of 100% yields a 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 uses a specific verb and resource: 'Add a Custom Data widget to a page.' It clearly identifies the widget type, which distinguishes it from sibling tools like add_data_widget, add_button_widget, and add_text_widget. It also adds the purpose of the widget (showing demo data until connected to a CSV dataset), making the tool's role unambiguous.

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 gives clear context for when to use this tool: to add a new Custom Data widget, then later connect it to a dataset via update_custom_data_widget. It mentions related tools (list_custom_data, get_custom_data) that support the follow-up workflow. It does not explicitly state exclusions or compare against sibling add_*_widget tools, but the context is sufficient for an agent to select it.

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