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

Annotations already declare the safety profile (non-readonly, idempotent, non-destructive), so the description's value is in the mechanics it adds: the session can be reused, and every texel_render output streams into the open browser tab. That live-relationship context is not derivable from structured fields. It doesn't cover session lifetime/teardown, hence not a 5.

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 the verb and the returned artifact, then rationale, then the call instruction. Three sentences carry their weight, though 'so they can watch the skin evolve and give feedback mid-way' is mildly verbose.

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 two-optional-param tool with an output schema and annotations, the description covers purpose, when to call, and the key live-render behavior. Return-value details are rightly left to the output schema, leaving little 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?

Schema description coverage is 100%, so the open and port parameters are fully documented in the schema. The description adds no parameter detail, so the baseline of 3 applies.

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 ('Start (or reuse) a live session and return a studio URL'), and the live-preview purpose is distinct from the batch siblings like texel_render. An agent can tell what this tool does 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 clear timing guidance ('Call it before the first render and share the URL with the user'), which is the key usage decision. It does not state when not to use it or name a competing sibling explicitly, so it stops short of a full 5.

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