glass_capabilities

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

Annotations already declare readOnlyHint=true, so the description doesn't need to repeat that. It adds valuable behavioral context: the tool is static (no session required), reports live status with specific enum values, and explains what each status implies (e.g., degraded means reduced fidelity, requires_setup means a setup step is missing). This goes beyond the annotations by detailing the response semantics.

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 dense but well-structured, front-loading the purpose and then explaining the status values and parameter usage. It's a bit long but every sentence adds value, explaining the status enum and the `tools` field. The structure is logical: purpose, status explanation, parameter guidance.

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 read-only capability check tool with a single optional parameter and no output schema, the description is quite complete. It explains the status values, what they mean, and how to use the parameter. The only minor gap is that it doesn't explicitly state the return format beyond the status and tools fields, but given the tool's simplicity and the annotations, this is sufficient.

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 already provides 100% coverage of the `backend` parameter, including valid values and the behavior for omitted vs. invalid names. The description adds a brief note about omitting for the active backend, but the schema already covers this. Since schema coverage is high, the baseline of 3 is appropriate.

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 tool reports which operations can be performed on a backend, listing specific operations (input, multi-touch, clipboard, accessibility, window move/resize) and the purpose (check before acting to avoid Unsupported errors). It distinguishes itself from siblings by focusing on capability reporting rather than performing actions.

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 explicitly says to use this tool to check capabilities before acting, and explains the status values and what they mean for subsequent tool calls. It also specifies when to pass the `backend` parameter and when to omit it, providing clear guidance on usage.

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