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

With readOnly/openWorld/idempotent annotations already covering safety, the description goes far beyond them: it discloses response shape, the meaning of compatibility_codes, the rule that unknown legs are never paired, how skipped counters behave, and that safety fields can be non-empty even when matches exist. This is rich behavioral context an agent needs beyond the annotations.

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 dense and long, but every section (modes, response, safety fields, codes, counters) adds operationally necessary information. It front-loads the core purpose and then layers detail; it could be more scannable with formatting, but it is not 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?

There is no output schema, so the description has to carry the return-value burden — and it does: it explains the per-leg prices, top_spreads_pp, compatibility_warning, codes, skipped counters, temporal_alignment, and low_confidence_pairs. For a three-parameter tool with a complex response, this is complete enough for an agent to call and interpret it 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%, so the baseline is 3; the description adds real value by explaining the topic shortcuts list, the override semantics of kalshi_event_ticker and polymarket_event_slug, and how the two modes interact. It doesn't redefine the schema but clarifies usage semantics sufficiently.

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 names a specific resource — the spread between Kalshi and Polymarket outcomes for the same resolving question — and gives the exact verbs: compute/compare and report compatibility. It is clear and specific, but it never names a sibling or says 'use this instead of X', so differentiation from polymarket_arbitrage or compare_entities is implicit rather than explicit.

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 two-mode explanation ('topic' vs explicit ticker/slug) tells the agent exactly which parameters to supply for which scenario. The closing warning that most pre-mapped topics return compatibility_warning and that 'pre-mapped ≠ tradeable' is a strong when-to-be-cautious cue, but no alternative tool is named for cases where this comparison is the wrong choice.

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