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

Annotations already declare read-only, idempotent, non-destructive behavior, so the description rightly spends its words elsewhere: a hard result cap ('at most 20 matches'), a data start date, and an explicit warning that coverage varies by dataset. These are non-obvious traits an agent cannot get from 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?

Three tight clauses with no filler: purpose plus result cap first, then temporal coverage caveats, then the routing hint to days_available. Front-loaded and appropriately sized for the tool's simplicity.

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 two-parameter read with no output schema, the description covers the essentials an agent needs to call it correctly: exact-match semantics, a result ceiling, the earliest available date, and a variability warning. It stops short of saying what happens if a symbol matches multiple mints across the day, which would have closed the remaining gap.

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 50% — mint_or_symbol has no schema description at all, and the description partially compensates by specifying 'exact' matching (meaningful for symbol vs mint disambiguation). The day parameter is documented in the schema, including its default, so the description adds little there.

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 and resource ('Public graduate facts'), the lookup key ('exact mint or symbol'), and the scope ('one UTC day'). The 'exact' qualifier separates it from broader listing tools, though it never names the closest sibling (coin_trades) to draw the contrast.

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?

It routes the agent to days_available when it needs the valid date range, which is a real usage instruction. However, there is no guidance on when to prefer this over coin_trades or day_full_stats, so the agent must infer the boundary from names alone.

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