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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds useful behavior beyond that: what the response contains (example, cell count, background, how to attach photos) and the handoff sequencing to make_shape_collage. It stops short of saying whether the plan is persisted or paginated, so not a 5.

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 short sentences with the purpose, the trigger and the follow-up ordered front to back. Every clause carries information an agent needs; nothing is repeated from the schema.

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 read-only preview tool whose complex nested shape object is fully documented in the schema, the description supplies what the schema cannot: the workflow position and the carry-forward rule. No output schema exists, and while it lists the kinds of content returned, some detail on the plan output would make it fully self-sufficient.

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 coverage is 100% and the nested shape object already carries examples and enum semantics, so the schema does the heavy lifting. The description only adds the rule that the same shape and background must be reused in make_shape_collage, which is a workflow constraint rather than new parameter meaning.

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?

States a specific verb and resource: shows the plan (shape, photo count, background) for the chosen collage, plus a real example and attach instructions. It is clearly distinguishable from make_shape_collage, which is named as the separate render step.

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?

Gives an explicit trigger (user picked a shape but has not attached photos yet) and an explicit next step (after attaching or sharing links, call make_shape_collage with the same shape and background). The alternative and the condition selecting it are both named.

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