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

Description adds substantial behavior beyond the readOnly/openWorld/idempotent annotations: it discloses the token-overlap matching method, the requirement to read compatibility_warning/compatibility_codes even when pairs exist, the precise meaning of temporal_alignment null, the gross-vs-net fee limitation, and ignored 'unknown' legs. No statement contradicts 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?

The first sentence fronts the core purpose and the rest is organized under clear headings (TWO MODES, RESPONSE, SAFETY FIELDS) with deliberate repetition only where safety matters. It is long, but most lines carry unique operational information that no output schema is there to provide.

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 complex 3-parameter tool with no output schema, this is unusually complete: it documents modes, response structure, safety codes, per-leg flags, skipped comparison counters, fees, and the false-positive caveat. An agent can invoke either mode and interpret the return correctly without external docs.

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 already covers all three parameters, so baseline is 3; the description adds real value by defining the 10 topic values, clarifying that both modes run the same matcher, and explaining that explicit ticker/slug override the topic-mapped side. It does not add new parameter syntax, but it gives decision-relevant semantics 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?

Opens with a specific verb phrase ('Cross-venue spread between Kalshi and Polymarket...') that names the exact resource and analytic task, and immediately sets it apart from single-venue Polymarket sibling tools by fixing the comparison to the 'same resolving question.' The two modes are also stated up front, so an agent can tell what the tool operates on without opening the schema.

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 two-mode explanation gives concrete decision criteria: use topic for the 10 listed shortcuts, use explicit kalshi_event_ticker + polymarket_event_slug for custom pairings, and the caution that pre-mapped topics often return compatibility warnings sets expectations. It does not explicitly name what to use instead when a different kind of cross-venue analysis is wanted, so it stops short of a full when/when-not guide.

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