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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds the crucial cost and side-effect guarantee: nothing is drawn or charged until the user presses send on the site. That is exactly the non-obvious behavior an agent needs to reassure a user about.

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?

Two sentences, front-loaded with the usage condition and ending with the return value and cost guarantee. Dense and nearly waste-free, though the first sentence is a long clausal 'or ... or ...' chain that could be tightened.

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?

Output schema exists and annotations cover safety/idempotency, so the description only needs to explain the trigger conditions and what the link does — both are covered, including the no-charge caveat. Nothing an agent needs to call this correctly 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?

Only one parameter, and the schema documents it fully (building type, rooms, sizes, storeys, plot, any language). The description adds no format or content guidance for 'brief' beyond that, so the schema does all the work — baseline 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?

States a specific verb and resource (prepare a link that opens the Plan Chat CAD studio) and scopes it precisely: for users who want a CAD DXF/DWG floor plan but aren't signed in here or prefer the website. The conditions cleanly separate it from start_cad_drawing-style in-app generation without needing the schema open.

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 three concrete triggering conditions (not signed in, prefers the website, wants to attach a sketch there), which is explicit when-to-use guidance. It never names the in-app alternative (e.g. start_cad_drawing) so the routing is implied rather than stated.

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