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

Beyond the readOnly/idempotent open-world annotations, the description discloses many non-obvious behaviors: compatibility_codes semantics, pairing_unverified being set whenever pairs are returned, unclassified legs never being paired, null temporal_alignment meaning 'could not be computed' rather than 'aligned,' and fees being gross rather than net tradeable edge. This is rich, useful behavioral context with no contradiction to 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?

The description is long but front-loaded with the core purpose and modes before going into safety details and response fields. Most sentences carry unique operational information, and there is no fluff. It could be tightened, given its density, but the length is largely justified by the complexity of the output and compatibility semantics.

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. It enumerates the response components: leg-by-leg prices, top_spreads_pp, compatibility_warning/codes, skipped counters, temporal_alignment, fees_note, and per-entry flags. It also explains null semantics and the meaning of each compatibility code. This is more than enough for an agent to understand what the tool returns and how to interpret it.

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?

All three parameters already have clear descriptions in the schema (100% coverage), so the baseline is 3. The description adds context about how the parameters combine—topic fetches a preset, explicit ticker/slug overrides the mapped side—and lists the valid topic values, but this is largely redundant or supplemental rather than essential. No parameter is left unexplained, but the description does not add substantial semantic depth beyond the schema.

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 precise statement of function: 'Cross-venue spread between Kalshi and Polymarket for the same resolving question.' It names the two venues, the comparison being made, and the underlying concept of price deltas on equivalent outcomes. It is clearly distinguishable from sibling tools like polymarket_arbitrage and polymarket_edges because it emphasizes the cross-venue, same-question comparison.

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 gives explicit mode selection guidance: topic mode for pre-mapped shortcuts, explicit mode for custom ticker/slug pairings, and clarifies that both modes run the identical token-overlap matcher. It also warns that most pre-mapped topics currently return compatibility warnings and that 'pre-mapped ≠ tradeable.' However, it does not explicitly contrast this tool against sibling tools for when one should be preferred over the other.

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