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

Annotations already mark the tool read-only, open-world, and idempotent, but the description goes far beyond that: it explains that legs with unknown metric_type are never paired, that temporal_alignment null means 'unable to compute' rather than aligned, that Kalshi fees are not modeled so spreads are gross, and exactly what each compatibility code means. This is substantial behavioral disclosure that materially changes how an agent should interpret results.

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 and dense, but it is organized into labeled sections (TWO MODES, RESPONSE, SAFETY FIELDS) and every sentence carries operational information needed because no output schema exists. It is front-loaded with the core purpose and trust caveat. It could be tightened, but the length is largely justified by the tool's complexity and safety 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?

For a tool with no output schema, the description is unusually complete: it covers input modes, safety fields, per-pair flags, skipped-leg counters, fee treatment, temporal alignment semantics, and the warning that compatibility_codes can be non-empty even with matched pairs. An agent has enough context to interpret results and avoid treating gross spreads as net tradeable edge.

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 baseline is 3; the description then adds meaningful parameter semantics by explaining the relationship between modes, that explicit ticker/slug overrides apply per side, and that both modes run the identical token-overlap matcher. It does not describe every possible value beyond the schema, but it clarifies how the parameters interact in a way the schema alone does not.

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 is explicit that the tool computes cross-venue spreads between Kalshi and Polymarket for the same resolving question, naming the resource and operation precisely. It explains two modes and what the response contains, but it does not explicitly differentiate itself from sibling tools such as polymarket_arbitrage or polymarket_edges, so it lacks the stronger sibling-contrast signal needed for a 5.

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 clear operational guidance: use `topic` for pre-mapped shortcuts and explicit `kalshi_event_ticker` + `polymarket_event_slug` for custom pairings. It also warns that pre-mapped topics are not automatically tradeable and that compatibility warnings must be read. However, it never contrasts when this tool should be preferred over sibling arbitrage/edge tools, so it stops short of explicit alternative-based usage guidance.

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