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

Annotations already declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=false, so the mutation/non-idempotent profile is known. The description adds the 'after today' constraint, but does not explain what happens on a duplicate add or a rejected date, which matters given non-idempotence.

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 short sentences, no filler, with the date constraint front-loaded before the parameter-sourcing note. Slightly terse grammar but nothing wasted.

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 2-parameter tool with annotations covering safety and no output schema, the description covers the essential constraint and ID provenance. It stops short of duplicate-handling or failure behavior, leaving a gap an agent would care about for a non-idempotent write.

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% — the date format lives in the schema but challenge_id has no schema description. The description compensates by telling the agent where challenge_id comes from ('as find_next_challenge and ladder give them'), which is real value beyond the structured fields.

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 ('Puts a challenge on a date') and adds the timing constraint 'after today'. It is distinguishable from remove_challenge and find_next_challenge by the write action, though it never names those siblings as the contrasting alternatives.

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?

Guidance is indirect: it routes the agent to find_next_challenge and ladder as the source of a challenge_id, and states the 'after today' constraint, but never says when to choose this tool over edit_schedule or schedule, nor what to do if the challenge is already on the calendar.

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