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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description still adds value by disclosing that the call returns null when no program is active and by summarizing the shape of what comes back. It does not discuss pagination or staleness, but for a no-arg read those are minor. No contradiction with the annotations.

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 sentences, zero filler. The primary behavior (retrieve the active program) is front-loaded, followed immediately by the sibling routing that prevents misuse. The parenthetical field enumeration is dense but earns its space by telling the agent what the payload contains.

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 an output schema present and 100% schema coverage, the description needs only to cover scope, null behavior, and tool selection – and it does all three. Nothing an agent needs before calling this no-arg read 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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline for a 0-param schema is 4. The description correctly spends no words on parameters and instead invests in return semantics.

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+resource ('Get the active training program') and goes further by enumerating the returned content (day templates, planned blocks/supersets, per-exercise targets) and the null case. It explicitly separates itself from get_coaching_context, review_program_draft, and import_document, so an agent can pick it 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?

The second sentence routes each adjacent intent to the correct tool: planning data to get_coaching_context(task='new_program'), draft validation to review_program_draft, and saving/replacing to import_document. The null-on-no-active-program clause tells the agent what to expect as a boundary condition, leaving nothing to inference.

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