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

Annotations declare readOnlyHint=false and openWorldHint=true, so the write/open-ended nature is already carried by structured data. The description adds the once-per-day limit and that 'Nil resolves it and answers', but says nothing about what happens to the submission, whether it can be retracted, or what the resolution looks like.

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?

Three tight sentences with the core action front-loaded and no filler. Every sentence contributes either the purpose, the constraint, or the response behavior.

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 write tool with no output schema, the description should cover the move format and the odd optional 'operator' field (how identity is resolved if omitted). 'One entry per operator' partially addresses identity, but enough is left unstated that an agent could call it with a malformed move.

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%: 'operator' is documented in the schema but the required 'move' parameter has no description anywhere. The description doesn't explain what a 'move' is or its expected format, so the single required input remains undefined. It fails to compensate for the coverage gap.

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?

'Submit your move for today's challenge' gives a specific verb (submit) and resource (move for the daily challenge). It is distinguishable from nil_daily and nil_standing, though it never clarifies how it relates to the similar-sounding transmit_to_nil, so sibling differentiation is only partial.

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 'one entry per operator per day' line implies the usage context and a hard constraint, which is helpful. But there is no explicit guidance on when to call this versus transmit_to_nil, nor what counts as a valid move, leaving the agent to infer.

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