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

Even with readOnlyHint, openWorldHint, idempotentHint, and destructiveHint already set, the description adds substantial behavioral context: it explains that legs with unknown metric_type or match_subtype are never paired, that compatibility fields can be non-empty even when matched_pairs > 0, that pairing is always keyword-based and unverified, and that null temporal_alignment means unknown rather than aligned. The fee disclosure stating that every spread is gross, not net tradeable edge, is especially valuable.

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 description is long but dense, with every section serving a purpose: modes, response shape, safety fields, compatibility codes, skip counters, and fee caveats. It uses uppercase labels and front-loads purpose before enumerating details. It could be restructured into clearer sections rather than one large prose block, but the length is largely justified by the tool's complexity and safety-critical interpretation rules.

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?

There is no output schema, so the description carries the full burden of explaining return values, and it does so thoroughly: leg-by-leg prices, top_spreads_pp, per-entry flags, compatibility fields, temporal alignment semantics, skipped leg counters, low_confidence_pairs, and fees_note. It also covers the null-means-unknown semantics and the unverified nature of pairing. For a comparably complex tool, nothing critical is missing.

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?

Although the schema already documents all three parameters at 100% coverage, the description adds meaning beyond the schema: topic is a curated shortcut list with examples, explicit kalshi_event_ticker and polymarket_event_slug override the topic-mapped side, and both modes run the identical token-overlap matcher. This prevents an agent from assuming different semantics for each mode.

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 opens with a specific statement: 'Cross-venue spread between Kalshi and Polymarket for the same resolving question.' It clearly names the resource, the computation, and the cross-venue scope, and it distinguishes this tool from same-venue or other research siblings by emphasizing cross-venue comparison. The two modes and response summary further reinforce what the tool does.

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 description clearly explains when to use the tool — for matching questions across Kalshi and Polymarket — and distinguishes the two invocation modes: pre-mapped topic shortcuts versus explicit ticker/slug pairings. It also gives important when-not guidance: pre-mapped topics often return compatibility warnings and are not automatically tradeable, and spreads are gross, not net of Kalshi fees. It does not explicitly name alternative sibling tools, so it stops short of a full 5.

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