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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is clear. The description adds valuable behavioral context beyond annotations by disclosing that an empty object is returned when no profile exists, which prevents the agent from misinterpreting an empty result as an error.

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?

The description is two sentences of dense, useful information. The first sentence lists the returned fields in a compact, scannable format. The second sentence adds usage timing and an edge-case behavior. No filler or redundancy.

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-parameter, read-only getter with an output schema, the description covers what is needed: what the tool returns, when to call it, and the special empty-object case. The presence of an output schema handles return structure, so no further detail is necessary.

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?

The tool has zero parameters, so there is no schema burden on the description. The description instead clarifies what the tool returns, effectively compensating for the absence of parameter semantics. It accurately summarizes the profile contents, making the no-parameter call sensible.

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 begins with a clear verb and resource: 'Get the user's saved Coach Profile'. It enumerates the specific fields returned (experience level, primary goal, training days per week, etc.), so the agent knows exactly what this tool provides. It is distinct from all siblings, none of which claim to fetch a coach profile.

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?

The description explicitly states when to use the tool: 'Call this early in a coaching conversation to ground advice in the user's stated goals, schedule, and equipment.' It does not name alternatives or exclusions, but there are no sibling tools that provide a similar coach profile, so the guidance is sufficient for correct selection.

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