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

Annotations declare readOnlyHint=true and these are consistent with a read-only analysis tool, so there is no contradiction. The description goes far beyond the annotations: it discloses that compatibility codes can be non-empty even on returned pairs, that unclassified legs are NEVER paired, that spreads are gross (not net of Kalshi fees), and that temporal_alignment null means 'could not be computed', not 'aligned'. This is exceptionally rich behavioral disclosure.

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 purpose is front-loaded in the first sentence and a clear mode/response/safety structure is visible. However, the description is very long, packing mode explanation, response format, safety codes, skipped-leg logic, fee disclosure, and feasibility warning into dense prose that interleaves topics. Every sentence earns its place — the content is genuinely useful — but the packing makes it harder to parse than it should be.

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 and no required parameters, the description carries the full burden of explaining return values and edge cases — and it does so comprehensively. It covers leg-by-leg prices, top_spreads_pp, compatibility_warning/codes semantics, skipped_unclassified and low_confidence_pairs, temporal_alignment fields, the gross-vs-net fee caveat, and the skipped_cross counters. Nothing an agent needs to interpret results correctly 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?

Schema coverage is 100%, so the schema already documents all three parameters. The description adds real value on top: it explains that topic picks from 10 pre-mapped shortcuts, that kalshi_event_ticker and polymarket_event_slug override the mapped side, and that both modes feed the identical matcher with the same disclosures. This clarifies the override relationship between topic and the explicit fields beyond bare schema text.

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 opening sentence states a precise verb and resource: computing the cross-venue spread between Kalshi and Polymarket for the same resolving question. This differentiates it from siblings like polymarket_arbitrage and polymarket_edges, which the title and context confirm are distinct tools, and the description's focus on same-question cross-venue comparison makes its scope unmistakable.

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 explains two modes (topic shortcuts vs explicit ticker/slug pairings), states that both run the identical matcher, and includes a frank feasibility warning that most pre-mapped topics return compatibility_warning today and that pre-mapped ≠ tradeable. This is strong usage guidance, though it never explicitly names sibling alternatives or states when NOT to use this tool versus a pure arbitrage or edge tool.

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