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

The description is unusually transparent: it explains that spread_pp is gross, does not model Kalshi's fees, that unknown legs are never paired, that null temporal_alignment means unknown rather than aligned, and that compatibility codes can be present on successful responses. It also defines machine-readable code meanings and the skipped-cross counters. This far exceeds what the readOnly/openWorld/idempotent annotations provide.

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 deliberately structured around modes, response, safety fields, skipped counters, and fee caveats, with the core purpose front-loaded. Some repetition exists — for example, the same compatibility codes are listed both as safety fields and as per-entry flags — but each repeated concept is central to correct interpretation. It is dense rather than padded.

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 a deceptively simple 3-optional-parameter input, the description carries a heavy burden and meets it. It specifies what the response contains (leg-by-leg prices, top_spreads_pp, fees_note, temporal_alignment), which failure modes exist, what null means, and how to interpret warnings. An agent can invoke this correctly without additional documentation.

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?

The input schema already documents all three parameters, so the baseline is 3. The description adds meaning beyond the schema by explaining the override relationship between explicit ticker/slug values and topic-mapped sides, and by stating both modes produce the same disclosures. It maps the parameter choices to exactly two behavioral modes.

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 names a specific resource and action: 'Cross-venue spread between Kalshi and Polymarket for the same resolving question.' It clearly contrasts across-venue pricing differences and says when bet shapes aren't equivalent the tool calls that out. It doesn't explicitly name a sibling to distinguish from, so it falls short of 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 explicit mode selection: the `topic` shortcuts auto-fetch events, while explicit `kalshi_event_ticker` + `polymarket_event_slug` allow custom pairings, and both modes run the same matcher. It also gives strong operational guidance: pre-mapped topics are often not tradeable and compatibility warnings must be read even when pairs exist. It stops short of naming alternative sibling tools, so a 4 rather than 5.

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