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

Adds value beyond annotations: 'reads only and changes nothing' reinforces readOnlyHint, and it discloses the account prerequisite plus the specific fallback behavior ('an account without a coaching brain gets the address of the coach console'). It doesn't mention rate limits or output format, but the output schema covers returns.

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 tight sentences, each earning its place: first the trigger and scope, then the safety and account requirements. Front-loaded with the use case.

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 zero-param read tool with an output schema, it covers the trigger, safety profile, account precondition, and fallback behavior. Nothing an agent needs to call it correctly is 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?

Zero parameters, so the baseline is 4. The description correctly implies no inputs are needed and focuses on what the call returns and its account prerequisites.

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 ('get my coaching brains') and enumerates what it returns: member counts, who went quiet, earnings, and note-sendability. This distinguishes it from siblings like find_coaching_brain (search) and send_note_to_my_members (write).

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?

Opens with 'Use this when a Phorme coach asks about their own coaching brains', clearly framing the trigger condition. It doesn't explicitly name alternatives like find_coaching_brain, but the 'own' framing and read-only nature differentiate it adequately.

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