analyze_screen_fields

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

With no annotations, the description carries the behavioral burden. It discloses that this is heuristic, operates on the current screen, and returns non-empty stripped lines with row numbers. The word 'Return' implies a read-only inspection, though it does not explicitly state that the screen is not modified.

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 definition is compact and front-loaded. The first sentence gives the core purpose, and the second adds the heuristic caveat and intended usage without extra fluff. 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 zero-parameter, read-only inspection tool with an output schema, this description is complete. It states what is returned, the heuristic nature, and why the AI would call it. No critical behavioral or contextual information 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?

There are zero parameters, so there is nothing for the description to clarify. The baseline for no parameters is 4, and the description correctly adds no unnecessary parameter details.

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 uses a specific verb and resource: 'Return a per-row inventory of non-blank content on the current screen.' This clearly distinguishes the tool from siblings like get_screen or find_text because it defines a unique result shape: per-row, non-blank, stripped content.

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 explicitly states the intended use: 'so the AI can locate input fields by neighboring labels.' It also warns 'Heuristic only', which sets expectations. However, it does not explicitly name alternatives or state when not to use this tool, so it stops short of full guidance.

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