list_effects

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

Beyond the annotations it discloses the opt-in nature, that each effect includes a preview, README and HyperFrames source, and that passing an effect returns its README and source. It does not contradict the annotations (nothing claims mutation). Remaining gap: the pagination/format of the list output is not described, but with no output schema the essentials are covered.

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 sentences, front-loaded with what the tool offers, followed by the gating rule and the parameter outcome. The parenthetical example list is slightly dense but earns its place by making the effect catalogue concrete.

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 one optional parameter, no output schema and sparse annotations, the description carries the needed weight: it explains what you get back (preview, README, source) and when to call. Only the shape of the returned list (count, ordering) is left implicit, which is minor for a simple lookup tool.

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 the schema already explains slug-or-name and empty-means-list. The description still adds value by stating the effect's return payload (README and source), which the schema does not say, clarifying the trade-off of passing the parameter.

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 concrete resource — ready-made effects for talking-head videos — with examples (text behind head, glass chart, freeze-frame sticker, tier list), so an agent knows exactly what it returns. It also distinguishes its two modes (list vs. single effect with README/source). It lacks an explicit 'list' verb, but the dual behaviour is unambiguous.

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?

Gives explicit when-to-use and when-not-to-use: 'call it only when the user names an effect or asks which effects there are, never to pick one yourself.' That is a strong, actionable routing rule that prevents speculative calls.

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