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

The description goes far beyond the readOnly/openWorld/idempotent annotations by disclosing that pairing is based on keyword overlap and is unverified, that spreads are gross rather than net of Kalshi fees, that compatibility warnings can appear even with matched pairs, and that null temporal_alignment does not mean aligned. This is exactly the kind of behavioral caveat an agent needs before trusting returned values.

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 labels like TWO MODES, RESPONSE, and SAFETY FIELDS, and nearly every sentence adds caveats or field semantics. There is some redundancy around token-overlap matching and temporal mismatch codes, but for a tool with no output schema and this much behavioral nuance, the density is largely justified.

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, the description carries the full burden of explaining response shape, and it does so unusually thoroughly: top_spreads_pp, compatibility_codes, temporal_alignment, skipped_unclassified, low_confidence_pairs, and fee disclaimers are all defined. It even explains what null means and warns that unmatched or unknown legs are never paired. The only minor assumption is that the caller supplies one of the two modes, but 'TWO MODES' makes that clear enough.

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 adds a meaningful layer by framing the parameters as two modes, explaining that topic is a pre-mapped shortcut and that the explicit pair overrides the topic-mapped side. This helps an agent reason about parameter combinations beyond what the individual schema descriptions provide.

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 concrete definition: 'Cross-venue spread between Kalshi and Polymarket for the same resolving question,' which makes the tool's function unmistakable. It clearly identifies the resource and the core computation, but it does not explicitly distinguish itself from sibling tools such as polymarket_arbitrage or polymarket_edges, so it stops 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 clearly explains the two invocation modes — pre-mapped topic shortcuts versus explicit kalshi_event_ticker + polymarket_event_slug for custom pairings — and gives practical guidance such as 'pre-mapped ≠ tradeable.' It sets expectations about when results may be unreliable, but it does not explicitly state when to prefer a sibling tool over this one.

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