browser_animation

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds traits they cannot express: an empty list vs null distinction for no-animations vs no-match, a ~6 s failure timeout with its error message, and an auth gate that blocks credential pages until user consent. These are exactly the operational behaviors an agent needs before calling.

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 ordered by importance: purpose and return payload first, empty/null semantics second, prerequisites and failure modes last. No filler; every clause carries distinct information.

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?

There is no output schema, so the description correctly compensates by enumerating the returned fields and the two empty-result variants. Combined with the documented failure and permission paths, an agent has everything needed to call this correctly.

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 description coverage is 100% and the single selector parameter is fully documented there, including the 'first matching element / document.querySelector' semantics. The description adds the phrase 'one element of the preview' but no further syntax or matching detail, so this is the baseline case where the schema does the heavy lifting.

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 ('Read the animations running on one element of the preview') plus the exact return shape (name, keyframes, computed timing), which clearly separates it from siblings like browser_dom or browser_eval. An agent can identify both what it does and what it returns without opening the 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?

Gives concrete preconditions: Reado's browser preview must be open with agent access, otherwise the call fails after ~6 s with a specific error string, and credential-bearing pages are refused pending user grant. It does not, however, name an alternative (e.g., that browser_eval could inspect animations differently) or state explicit when-not-to-use cases beyond the environment prerequisites.

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