streamfog_set_lens

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

The description reveals important behaviors: it resolves the lens identifier against a mapping file, falls back to a constructed action name, and dispatches an action. It also includes the return format. Annotations only provide readOnlyHint=false, so the description adds substantial context. However, it does not disclose authorization requirements or error handling.

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 concise, well-structured with sections for return format and examples. Each sentence adds value without redundancy. It is front-loaded with the core purpose.

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?

Given the tool's low complexity (one parameter, no nested objects) and the presence of an output schema, the description provides complete context: purpose, parameter behavior, fallback logic, return format, and examples. Nothing essential 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 sole parameter 'lens_identifier' is fully described in the schema (100% coverage), and the description adds meaningful details: how the identifier is resolved (against lenses.json), fallback behavior, and examples of valid values. This significantly aids correct invocation.

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 activates a specific AR lens or face filter. It uses a specific verb ('Activate') and resource ('AR lens or face filter'), and distinguishes from sibling tools like streamfog_clear_effects and streamfog_list_lenses.

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 describing the activation process, but it does not explicitly state when to use this tool versus alternatives like streamfog_clear_effects or streamfog_list_lenses. No when-not or sibling comparisons are provided.

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