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

The most valuable disclosure is that this replaces the coach's principles wholesale — the agent knows existing principles are overwritten, which annotations (idempotentHint=true, destructiveHint=false) do not convey on their own. The approval/confirmation gate is also real behavioral context. However, there is no statement about permissions, what happens to prior principles not re-sent, or failure modes on partial approval; since annotations already cover read/write and idempotency, this lands at a solid 3 rather than higher.

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 the when-to-use condition, then payload content, then the safety constraint last. Each sentence carries a distinct job with no filler.

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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. The description still supplies the essential non-schema facts: that the write is a full replacement and that confirmation is an approval gate. Only minor gaps remain (brain_id purpose, item-count bounds) and those are visible in the schema.

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 67% and the schema already documents sources and confirmation, so the baseline applies. The description restates the item shape ('short name, optional cue and why, and source links'), adding little beyond the property names, and says nothing about brain_id or the 40-item limit.

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 action (write the coach's approved principles) and resource, plus what each principle carries (name, cue, why, sources). It implicitly situates itself after a generation step ('the principles their agent wrote from their own reels, posts and words'), but never names a sibling like teach_my_coach or set_my_brain_rules, so the boundary is inferred rather than stated.

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 this when the coach has approved...' gives an explicit triggering condition, and 'Set confirmation to true only after the coach approved exactly these; never invent a principle' gives a clear prohibition. What is missing is any pointer to an alternative tool when the coach has not yet approved or when principles should be added rather than replaced.

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