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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, covering the safety profile. The description goes far beyond that: it details the matching logic (token-overlap matcher), the meaning of temporal_alignment_unknown ('NOT the same as confirmed-aligned'), the fees_note disclosing that reported spreads are gross and not net tradeable edges, and the compatibility warning codes (event_subject_mismatch, temporal_mismatch, etc.). It also explains that legs with unknown metric_type are never paired and land in skipped_unclassified or low_confidence_pairs. This adds substantial behavioral context beyond the annotations and does not contradict them.

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 well-structured with clear sections: TWO MODES, RESPONSE, SAFETY FIELDS, and counters. It front-loads the core purpose and then systematically covers matching, warnings, fees, and skipped categories. Every sentence carries information - there is little fluff. It could arguably be trimmed, but given the complexity of the tool and the absence of an output schema, the length is justified. It is not under-specified; it uses capitalization and section markers to improve readability. The structure earns a 4 rather than 5 because of its length, but it remains efficient.

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?

Given the tool's complexity - two modes, multiple safety fields, compatibility codes, temporal alignment semantics, fees disclosure, and skipped categories - the description covers all functional aspects an agent needs to invoke and interpret results correctly. There is no output schema, so the description carries the full burden of explaining the response structure, including top_spreads_pp, compatibility_warning, compatibility_codes, temporal_alignment, fees_note, and skipped counters. It also clarifies edge cases like null temporal_alignment and unclassified legs. Nothing critical is missing for the agent to call this tool effectively.

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% - each parameter has a description in the schema. The description adds value by explaining the topic list explicitly (listing all shortcuts), clarifying that explicit ticker/slug override the topic-mapped side, and noting that both modes run the identical token-overlap matcher. This goes beyond the schema's basic type/description by providing semantic relationships and usage context. While the schema already documents each parameter, the description enriches the meaning of how the parameters interact, so a 4 is appropriate.

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 purpose: 'Cross-venue spread between Kalshi and Polymarket for the same resolving question.' It clearly identifies the resource (spread between two venues) and the specific verb (compute/retrieve). It also distinguishes itself from sibling tools like polymarket_arbitrage and polymarket_edges by focusing explicitly on cross-venue comparison of the same question, and it further elaborates two modes (topic precuts vs explicit ticker/slug), leaving no ambiguity about 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 provides clear when-to-use guidance: it introduces two modes - topic shortcuts for common macros and explicit ticker/slug for custom pairings - and explains when each is appropriate. It also gives a critical usage warning: 'Real cross-venue spreads are rarer than the macro-shortcut list suggests — most pre-mapped topics return compatibility_warning today; pre-mapped ≠ tradeable.' This tells the agent when not to expect a tradeable spread and to verify matching. It also contrasts with siblings implicitly by being the cross-venue tool. The guidance is explicit about the conditions and caveats.

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