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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the mutation/safety profile is covered. The description adds valuable behavioral context beyond annotations: the widget has no datasource, never fetches, content is inline, and omitting the value defaults to 0. It also notes that position/width/height match the editor's card, which is useful placement context. Minor gap: it doesn't state whether adding is idempotent or what the response contains, but the output schema likely covers return values.

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?

Three sentences with no filler. The core purpose is front-loaded, the distinguishing behavior (no datasource, inline content) comes second, and the practical default/alternative guidance is last. Every sentence earns its place.

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 create-style tool with 5 params, 100% schema coverage, and an output schema, the description is nearly complete. It explains the widget's unique behavior, the default value, and the update path. It doesn't explicitly state prerequisites (e.g., that the page must exist) or whether the widget is immediately visible, but those are minor given the schema and output schema context.

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 100%, so the schema already documents all 5 parameters. The description adds meaning for 'value' (typed-in content, examples like 'R50' or 'Active', defaults to 0) and clarifies that source_id is the report ID, but it doesn't add much beyond the schema for name, page_id, or client_id. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Add') and resource ('Static Value widget to a page'), and clearly distinguishes it from sibling card tools by explaining it has no datasource and never fetches. It also names the sibling update_static_value_widget for later edits, so an agent can tell this tool apart from add_data_widget, add_goal_widget, etc.

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 explicitly says when to use this tool (to add a static KPI card with inline content) and contrasts it with 'the other cards' that have datasources. It also gives a clear alternative: omit the value to land on 0 and set it later with update_static_value_widget. This is explicit routing guidance.

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