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

Beyond annotations (readOnlyHint, idempotentHint), the description details that it performs one HTTPS read, has no destructive side effects, does not generate Natural Language, and never executes trades, wallets, or settlement flows. It also explains point-in-time recomputation logic and lookahead safety flags, adding significant behavioral context.

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 well-structured and front-loaded with purpose, then methodology, then parameters and behavior. It is somewhat long because it restates parameter names already present in the schema, but every sentence adds useful context, so it is not wasteful.

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 that an output schema exists and annotations are rich, the description covers purpose, methodology, behavior, and mode selection. It is complete enough for an agent to invoke the tool correctly without needing to infer additional context.

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?

With 100% schema description coverage, the baseline is 3. The description lists parameter names but adds no new semantic meaning beyond the schema, except for the 'mode' defaults and usage advice, which is already partially in the schema.

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 clearly states the tool returns daily ATLAS-7 CompanyFacts-derived factor rows keyed by as_of_date, with a specific methodology (filed <= as_of_date) that distinguishes it from other history tools. It also names concrete use cases (Mirror Pulse, backtests, agents), making the purpose unmistakable.

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 explicitly says to use this tool when Mirror Pulse, backtests, or agents need daily factor rows, giving clear context. It also provides mode selection guidance (compact for joins, full for audit pages) but does not name alternative tools or explicitly state when not to use it, so a 4 rather than 5.

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