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

With only a minimal annotation (destructiveHint false), the description adds meaningful behavioral context by explaining that the tool creates a proposal (→ Inbox) rather than directly modifying a screen, and how missing coordinates are handled. This goes beyond the schema and annotation, though it still doesn't disclose return values or error conditions.

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 two sentences with the core purpose front-loaded and a clear emphasis on the mandatory coordinate parameters via 'ALWAYS'. It is concise, direct, and avoids unnecessary detail.

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 10 parameters and no output schema, the description covers the primary operation, critical usage constraint, and proposal workflow. It leaves some gaps around return values and preconditions, but partially compensates for schema limitations with the coordinate explanation. This is close to complete but not fully comprehensive.

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 80%, but the description adds crucial semantics for x/y/w/h by specifying they are in pixels on the screen's resolution from get_screen and that omitting them results in an unplaced pile. This enriches the meaning of these parameters beyond the schema's basic descriptions.

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 clearly identifies the tool as proposing an element onto a screen, with a specific verb and resource, and indicates that it goes to an Inbox. It distinguishes from sibling tools like propose_screen and propose_system by focusing on element-level UI additions and emphasizing coordinate requirements.

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?

It provides explicit usage rules, such as 'ALWAYS pass x/y/w/h' and the behavioral consequence of omitting coordinates ('unplaced pile'). The 'SECONDARY (user-driven UI)' label gives some context for when to use it, but it does not name alternative tools or state when not to use it, so it lacks the strongest differentiation.

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