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

Even with readOnly/openWorld/idempotent annotations, the description adds substantial behavioral disclosure: compatibility_warning/codes, pairing_unverified, gross vs net spreads via fees_note, skipped_cross_type/subtype counters, and the rule that unknown legs are never paired. It even clarifies the subtle semantics of temporal_alignment null versus unknown. No contradiction with annotations exists.

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 front-loaded with the core purpose and is information-dense with no filler, but it is a long single block of text with nested parentheticals and code-inlined caveats. Every sentence earns its place, yet structure and scannability would benefit from bullets or section breaks. The length is somewhat justified by the absence of an output schema, but it is not concise.

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 return values, and it does so thoroughly: leg-by-leg prices, matched top_spreads_pp, compatibility_codes, skipped categories, fees_note, and temporal_alignment semantics. It also warns about the rarity of real spreads and the limits of pre-mapped topics. An agent has enough detail to invoke and interpret the tool correctly.

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% and each parameter already has a description, so the baseline is 3. The description adds valuable semantics beyond the schema by explaining that topic auto-fetches the matching event on each venue, that explicit fields override the topic-mapped side, and that both modes run the identical token-overlap matcher. This lifts it above baseline.

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 first sentence states a specific operation and resource: computing the cross-venue spread between Kalshi and Polymarket for the same resolving question. It goes on to define two distinct modes and what the response contains, making the tool's purpose unmistakable. The cross-venue scope also separates it from siblings like polymarket_edges or polymarket_arbitrage even without naming them.

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 usage context: use the topic shortcuts for pre-mapped macro events, or supply explicit kalshi_event_ticker and polymarket_event_slug for custom pairings. It also provides important expectations, such as 'pre-mapped ≠ tradeable' and that most topics currently return compatibility_warning. It does not explicitly compare against sibling tools or state when NOT to use it, which prevents a 5.

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