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

Annotations already cover the read-only safety profile, yet the description adds substantial behavioral context: every entry belongs to an installed extension, platform values map to hub/builder/render, and it discloses hard limitations (cannot open or read the embedded page, cannot attribute an entry to a contributing extension). That limitation disclosure is exactly what an agent needs before promising a user anything.

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?

Front-loaded with what the tool does, then field semantics, then limitations, then the alternative. Dense and mostly earning its length, though the three quoted rhetorical questions add a little padding that plain use-case phrasing would have covered.

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?

With no parameters and no output schema, the description carries the burden of explaining returns — and it does, covering platform/type/attachedTo and explicitly bounding what cannot be known. Nothing an agent needs to call it 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?

The tool takes zero parameters, so the baseline is 4. The description goes further by explaining the meaning of returned fields (platform, type, attachedTo), which is useful even though it is technically output rather than input semantics.

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 (list the screens extensions add to apps) and grounds it in recognizable symptoms ("where did this new menu item come from", "what is this extra block on the product page"). It explicitly separates itself from get_installed_extensions, so an agent can pick the right one without opening either schema.

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?

Names the alternative and the condition that selects it: "To go the other way — what is installed at all — use get_installed_extensions." The motivating questions imply when to reach for it. It does not address the similarly named flow_list_extension_surfaces sibling, leaving a small ambiguity.

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