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

With readOnlyHint/openWorldHint/destructiveHint already covering the safety profile, the description adds genuinely new behavioral context: 'Free public', 'No API key required', and that outputs carry explicit as-of timestamps and volume bases. These tell the agent about access requirements and data provenance beyond the annotations. No return-format or rate-limit detail is added, so not a 5.

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?

Two sentences, front-loaded with the resource and its contents, then the usage rule. The field enumeration is dense but each item is substantive and earns its place. Slightly list-heavy but 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?

For a read-only metadata endpoint with an output schema, the description need not explain return values, and it covers scope, contents, and usage rationale. An output schema exists and annotations carry safety, so the remaining burden is low. Adequate and nearly complete.

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% for the single fiat parameter, so the schema already documents it fully (default usd). The description's mention of 'currency basis' loosely relates but adds no syntax or constraint detail beyond the schema. Baseline 3 is correct when the schema does the heavy lifting.

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 (methodology and comparable coverage for every prediction-market venue) and enumerates what it returns: source kind, supported metrics, market counts, volume bases, currency basis, comparability, timestamps. That is far more than a restated name. It stops short of differentiating itself from close siblings like pm_data_sources_health or pm_data_overview, so an agent must infer the boundary.

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?

It gives explicit, actionable context: 'Use this before comparing venue totals so a completed-day figure is never described as rolling 24h and play-money points are never described as USD.' That is clear when-to-use guidance tied to a concrete failure mode. It does not name alternatives or state when-not-to-use, so it falls short of a 5.

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