Lottery: round, jackpot, tickets sold, next draw, how to buy, the 1st, 2nd and 3rd prize with their odds, the last five results. With round: that draw's number, its proof and every ticket.
| Name | Required | Description | Default |
|---|---|---|---|
| round | No | optional: one round, like 2026-W42 or 2026-10-12 | |
| format | No | text (default) or json |
Changes observed during successful MCP inspections.
Input schema / properties / roundAdded value: +{
+ "description": "optional: one round, like 2026-W42 or 2026-10-12",
+ "type": "string"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, and it does disclose the payload shape (jackpot, tickets sold, prizes with odds, last five results) which is valuable given there is no output schema. However it says nothing about read-only status, auth/cost requirements, rate limits, or that it deliberately does not purchase tickets, which is notable given the lottery_buy sibling.
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?
It is compact, but it opens with 'Lottery:' which merely restates the tool name and then delivers a dense comma-separated list of fields with no structure or prioritization. Front-loading is weak because the round-conditional behavior, the most actionable part, sits at the very end.
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 no output schema, the description usefully substitutes by enumerating the returned fields, and both parameters are documented in the schema. For a simple two-parameter read tool it is nearly complete, lacking only an explicit statement of read-only behavior and the no-round default payload.
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 100% so the baseline is 3, but the description adds real meaning beyond the schema: the round parameter's effect is spelled out as 'that draw's number, its proof and every ticket', which is not derivable from the schema's format examples alone. The format enum is left to the schema, which is fine.
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 names a specific resource (the lottery) and enumerates exactly what it exposes: jackpot, tickets sold, next draw, how to buy, prize tiers with odds, last five results. That is clear enough to separate it from a data-fetching read tool versus the sibling lottery_buy, though it never uses an explicit verb (e.g. 'returns'/'fetches') and never names lottery_buy as the contrasting action.
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?
Usage is only implied through the conditional 'With round: that draw's number...' which tells the agent that supplying round switches to a single-draw view. There is no explicit when-to-use/when-not-to-use guidance and no mention of when to call lottery_buy instead of this tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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