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

Annotations already mark the tool read-only, idempotent, and non-destructive. The description adds substantial behavioral detail beyond that: null qoq/turnover/activity_counts for first-time quarters, count conditions never matching nulls, a _warnings signal for multi-quarter results, page x page_size <= 500, dynamic credit cost charged even for empty results, the Pro plan requirement, and the EDGAR URL behavior.

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 long but information-dense and front-loaded with the core purpose before listing output fields and constraints. Each clause adds operational detail (pagination limit, cost, plan, endpoint, EDGAR URL semantics). It is structured enough to be navigable, though slightly dense.

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?

With no output schema, the description carries the burden of explaining return values, and it does so thoroughly: row granularity, field list, null semantics, multi-quarter warnings, pagination limits, cost, plan requirement, and endpoint. For a 10-parameter screener with no output schema, this is a complete and actionable definition.

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%, so the schema already documents all 10 parameters. The description adds some useful context, such as 'count conditions never match it' for null quarters and the default full listing behavior, but most parameter-level meaning is already in the schema. This is the baseline 3 case where 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 opens with a specific verb and resource: 'Screen SEC Form 13F institutional filings across the whole library.' It clearly defines the output granularity ('one row per manager-quarter') and lists the headline fields returned. This distinguishes it from single-manager or filing-specific sibling tools like get_institutional_portfolio or get_event_filing.

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 gives clear usage context: an empty body returns the full listing, it scans the whole library, and it explains quarter-over-quarter null behavior. It does not explicitly name alternatives or say when not to use this tool, so it stops 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.