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

Annotations only indicate it is not read-only and not destructiveasi no contradiction. The description adds meaningful behavioral detail: the widget initially shows demo data, returns a new widget_id, and has position/size behavior matching the editor's Custom Data card. This goes beyond what the annotations reveal.

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 concise and front-loaded: it states the action, the initial state, the return value, and the follow-up configuration steps in a tight, logical flow. Each sentence contributes necessary information without redundancy or filler.

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 only three required parameters and an output schema, the description covers the key context an agent needs: what the widget does initially, what the return value is, how to configure it next, and where to get the required IDs and column names. No crucial information 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 has 100% description coverage for all three required parameters, each sourced from list_pages, list_clients, or list_reports. The tool description does not add extra parameter-level meaning, so the baseline of 3 is appropriate.

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 Custom Data widget to a page', and describes its behavior as 'a table showing demo data until it points at an uploaded CSV dataset.' This clearly distinguishes it from related sibling tools like add_data_widget or add_button_widget, which serve different widget types.

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 workflow context by explaining that the returned widget_id should be used with update_data_widget, and where to get advanced.custom_data_id and column names. It does not explicitly list exclusions or alternatives, but the focused purpose and follow-up configuration make the intended usage clear.

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