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

Annotations already declare readOnlyHint=false, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered without the description. The description adds no behavioral context of its own: nothing about whether the switch persists across sessions, affects other concurrent work, or what happens when an unknown id/name is supplied.

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?

Two short sentences with no filler, and the core action is front-loaded before the usage hint. Nothing can be trimmed without losing 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?

For a simple two-parameter toggle with no output schema and annotations covering safety, the description is adequate. The notable omission is parameter interaction semantics (id vs name precedence/mutual exclusivity) and any note on the effect or failure mode of the switch.

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%, so both parameters are already documented, giving a baseline of 3. The description's 'by id or name' adds slight clarification of intent, but with zero required parameters and two optional ones it never resolves the ambiguity of what happens if both are supplied or whether they are mutually exclusive.

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 states a specific action ('Makes another brain the active one') and the two lookup keys ('by id or name'), which is enough to distinguish it from brain_list, brain_current, and brain_create. It is close to the title 'Switch active brain', but the added 'another brain' and lookup-key detail lift it above pure restatement.

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?

'Use when the user wants to work in a different brain' gives a clear triggering condition. It stops short of naming alternatives (brain_current, brain_list) or stating when not to use it, so it is clear context without exclusions.

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