Get App Icon

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

Annotations already mark this read-only and idempotent, and the description reinforces that with 'Read-only.' Beyond annotations, it discloses the underlying ECP endpoint, the exact image dimensions, the base64/data URL return format, and the special 'dev' app id — genuinely useful behavior context for a tool with no output schema.

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 tightly packed sentences with no filler. The core operation and format come first, followed by id discovery, then the explicit sibling distinction. 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 simple two-parameter read-only tool, the description covers the return format, endpoint, id discovery, default-device behavior (implied by the schema's optional device param), and the key alternative (screenshot). Nothing an agent needs to invoke 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?

Schema coverage is 100%, and both parameters already include examples and guidance ('837' for YouTube, device IP/serial examples). The description adds the 'dev' shortcut and ECP route hint, but the schema already carries the semantic load, so the added value over the schema is modest.

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 ('Fetch'), a precise resource ('336x210 app icon for one installed channel'), and the returned format ('base64 / data URL'). It also distinguishes itself from screenshot by naming what it is for (previewing branding) versus capturing the current screen.

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?

Explicitly tells the agent when to use this tool (previewing a channel's branding) and when not to (use screenshot for the current screen). It also tells the agent how to discover valid app ids via ecp_query or launch_app's notes, leaving no ambiguity about prerequisites.

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