Get screen image

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds a key behavioral trait: the image URL is resolved from Terminus and cannot be supplied by the caller. This goes beyond the annotations and clarifies a constraint that affects how the tool is invoked.

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 a single, concise sentence that front-loads the action and resource, then adds a critical constraint. Every word earns its place; there is no fluff or repetition of schema or annotation information.

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 tool is simple with one parameter and no output schema. The description covers the core purpose and the URL constraint, but it does not explicitly state what the tool returns (e.g., image data vs. image URL). Since no output schema exists, the description should clarify the return format for full completeness.

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?

The schema provides the parameter name 'screen_id' with type and constraints, but no description. The tool description references 'a listed Terminus screen' which indirectly associates the parameter with the screen, but it does not explicitly state that screen_id is the identifier. With 0% schema description coverage, the description only partially compensates.

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 states the action ('Fetch') and the resource ('rendered image for a listed Terminus screen'). It distinguishes this tool from siblings like read_screen_doc and get_display_context by focusing specifically on the image. The additional note that the URL cannot be caller-supplied adds further precision.

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?

The description implies usage by mentioning 'a listed Terminus screen', which suggests the screen must come from list_screens. However, it does not explicitly state when to use this tool over alternatives like read_screen_doc or get_display_context, nor does it provide exclusions or prerequisites beyond the screen being listed.

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