Add an element

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

Beyond the annotations (which are all false and give no safety hints), the description richly discloses behavior: 'Omit x/y and the layout engine places it', 'the geometry is computed for you', and 'This does not display anything. Call render_scene once your edits are done.' It also explains that parentId nests the element inside a group. These are meaningful behavioral traits not present in annotations or schema descriptions.

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 well-structured and front-loaded: a one-sentence summary, a bold 'USE THIS' callout, then prerequisites, special cases, and rendering note. Every sentence adds unique value—no fluff or repetition of schema content. It is compact despite covering multiple scenarios (first-time adds, connections, layout, grouping, rendering).

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 remarkably complete for a tool with nested objects and 3 parameters. It covers prerequisites (get_scene), the exact workflow for linking elements (connection type), layout behavior (omit x/y), grouping (parentId), and the follow-up step (render_scene). Since an output schema exists, the lack of return-value explanation is acceptable. The tool feels self-contained for an agent to invoke successfully.

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 parameters are well-documented in the schema. The tool description nevertheless adds significant value: it explains that the element object is 'exactly the same shape as the entries of elements in render_diagram', provides a concrete example, and clarifies behavior of x/y (omit for auto-layout). This goes beyond the schema, though the core parameter meanings are already covered, so a 4 is appropriate rather than 5.

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 a clear, specific statement: 'Add one element to a scene that already exists.' This uses a strong verb ('Add'), defines the resource ('element'), and the target ('scene'). It distinguishes itself from sibling tools like update_element, remove_element, and group_elements by focusing solely on adding new elements. Concrete usage examples ('add a load balancer', 'draw an arrow from A to B') further clarify the purpose.

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?

Explicit 'USE THIS' guidance tells the agent exactly when to apply the tool: 'when the user wants something new in a diagram you already drew.' It also provides alternative and prerequisite actions: 'Call get_scene first if you are not certain which ids exist' and 'Call render_scene once your edits are done.' The connection workflow is explained with 'make a second call with an element of type 'connection'', giving clear usage boundaries.

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