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

Annotations already declare read-only, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds two genuinely useful facts beyond that: the explicit per-call price ($0.002/call) and the exact return shape (items[] with volume, open interest, liquidity, top_outcomes with yes_prob). It does not disclose pagination behavior, whether 'most active' is a fixed ranking or tied to limit, or what happens when filters match nothing.

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?

The response-shape notation is front-loaded in one dense clause, followed by filters, price, and the usage cue — no filler sentences. The items[] enumeration is heavier than prose would be, but it earns its place because there is no output schema to document return fields.

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 inline return-field map is a meaningful contribution, and pricing plus the event-group definition round out what an agent needs to select and call this tool. The remaining gaps — undocumented limit, undefined filter semantics, no pagination or empty-result behavior — are modest for a read-only three-parameter lookup.

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 description coverage is 0%, so the description bears full responsibility for parameter meaning, and it only partially delivers. It names 'Filters q, tag' without saying what q matches (keyword? title?) or what form tag takes (slug, ID, free text). The third parameter, limit (1-50), is never mentioned at all, leaving its cap and default undiscoverable from prose.

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 and scope: 'most active Polymarket events' with an explicit definition of an event as 'event groups (all outcomes of one question family) with open interest.' That conceptual framing lets an agent distinguish it from market-level siblings like polymarket_markets or polymarket_top without opening schemas. It stops short of naming any sibling outright, so the differentiation is inferential rather than explicit.

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 closing sentence ('Use for Polymarket event groups... with open interest') gives a positive usage signal, implying this is the right tool when you want aggregated outcomes per question. There is no when-not guidance, no mention of when to prefer polymarket_markets or polymarket_context instead, and no note on result limits or cost-driven alternatives.

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