fetch_ff_factors

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

With no annotations provided, the description carries full burden. It discloses that data is freely available from an external source, describes the return format, and notes decimal values. However, it does not explicitly state idempotency, latency, or any side effects, though the operation is clearly read-only.

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 with a clear title line, context paragraph, and explicit Args/Returns sections. Every sentence adds value, and there is no fluff or repetition. It is appropriately sized for a single-parameter tool.

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 one optional parameter and a rich return format described in the description text, the description is largely complete. It provides source attribution and use case. The absence of a formal output schema in the provided definition is compensated by the textual description of return fields.

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?

The only parameter, start_date, has a default value. The description adds meaning beyond the schema by explaining it filters dates on or after the specified date. This clarifies the parameter's purpose effectively.

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 'Download Fama-French 5-factor + momentum daily data.' It specifies the exact resource (Fama-French factors) and action (download), and the context of factor decomposition differentiates it from sibling tools like fetch_prices or fetch_financials.

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 mentions 'Used for factor decomposition in stress testing' which implies a use case but does not explicitly state when to use this tool versus alternatives, nor does it provide any when-not-to-use guidance. The usage context is implied rather than explicit.

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