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

Annotations already flag destructiveHint=true, readOnlyHint=false, and idempotentHint=true, so safety is covered. The description adds genuine effect semantics beyond that: joining carries the voice's memory along, and a null brain_id copies the shared memory so nothing relied on disappears, plus a same-account/team constraint.

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-loads the core action, then adds the null semantics and safety constraints. Every clause earns its place, though the sentences are dense enough that it is more thorough than minimal.

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 no output schema and rich annotations already present, the description covers behavior, constraints, and confirmation procedure adequately for a 2-param mutation. The unmapped profile_id is the only notable gap.

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 0%, so the description must carry the load; it does this well for brain_id (uuid from list_brains vs null detach and its copy semantics). profile_id is never mapped to "the voice," leaving one of two parameters to inference despite the low coverage.

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 ("Move a voice to another brain") and immediately scopes it against the sibling that supplies brain_id (list_brains). An agent can tell what this does and how it relates to list_brains without opening a 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 context: use brain_id from list_brains to join, pass null to give the voice its own brain, and only same-account/team brains qualify. Also instructs the agent to confirm with the user first. Lacks an explicit when-not-to-use beyond the account/team restriction.

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