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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so safety is covered. But the description adds nothing about mutation behavior: whether an existing day on the same day_of_week is rejected or overwritten, whether days are reordered, or what identifier comes back. For a 6-param creation tool that is a real gap.

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?

A single front-loaded sentence with no filler. It is efficient, but the brevity is partly under-specification rather than discipline.

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 6 parameters, no output schema and only partial annotation coverage, the description should say more: which fields are optional, how day_of_week collisions behave, and what the tool requires (an existing week from get_program). As written, an agent must infer all of this.

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 only 50% – warmup_notes, cooldown_notes and estimated_minutes are undocumented anywhere. The description mentions no parameters at all, so it does not compensate for the coverage gap or clarify semantics like day_of_week indexing beyond what the schema already says.

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 concrete verb ("Adds") and resource ("a training day") plus its placement ("to a week of a program"), which distinguishes it from add_program_week (adds a week) and add_exercise_to_program_day (adds an exercise to a day). It stops short of naming those siblings explicitly.

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?

No guidance on when to use this versus update_program_day (existing day) or add_program_week. The only hint that weekId must come from get_program lives in the parameter schema, not the description.

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