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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is known. The description adds valuable context beyond annotations: it explicitly states the tool 'does not fetch live exchange state or write recorder artifacts on demand,' and clarifies that the data is 'persisted' and 'venue-pure.' This enriches the behavioral model without contradicting 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 compact (four sentences) and well-structured: opening use-case statement, return content, parameter overview, and behavioral note. It front-loads the most important information and avoids redundancy with the schema. Every sentence contributes useful context, making it a model of concise tool documentation.

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?

Given the tool has a rich output schema and fully documented parameters, the description need not repeat return details. It covers the core purpose, output components, optional modes (compact/full), and behavioral constraints. Minor gaps remain, such as not clarifying the relationship between source_date and source_date_from/to, but overall it is sufficiently complete for an agent to invoke 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 description coverage is 100%, and each parameter already has a detailed description in the schema. The description merely lists parameter names (product, source_date, source_date_from/to, underlying_ticker, mode, limit, offset) without adding new semantics, such as mutual exclusivity or mode differences. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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 uses a specific verb ('returns') and resource ('persisted Coinbase INTX market-factor history for one perp product'), and lists concrete output contents (factor rows, deltas, quality state, optional full market inputs or lineage). It clearly distinguishes this tool from sibling tools like calculation_history or rankings by emphasizing 'venue-pure factor history' for a single product.

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 opens with an explicit when-to-use statement: 'Use this read-only tool when the user wants persisted Coinbase INTX market-factor history for one perp product.' It also clarifies what it does not do (fetch live exchange state, write recorder artifacts). However, it does not name alternative sibling tools or provide explicit when-not-to-use guidance, so it falls just short of a full 5.

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