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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds substantial behavioral detail: the delta calculation, inclusion of new and sold-out positions, the condition that a previous holder only counts if it filed for the target quarter (with CIK migration/deregistration caveat), the open-window limitation, and the markdown table output with two sections. This goes well beyond 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 dense but well-organized: core purpose first, then the mechanics of how the data is computed, then edge cases, then output format, and finally usage guidance. Every sentence earns its place, and there is no redundancy or filler. It reads naturally and front-loads the most important information.

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?

The tool involves quarterly comparison logic and edge cases (filing windows, CIK migration), and the description covers these thoroughly, including the output format (markdown table with two sections). However, it does not specify the exact columns or structure of the returned table, which might be needed for downstream processing. Given the lack of an output schema, this is a minor omission but not critical for selecting the tool.

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?

All three parameters (ticker, maxResults, reportDate) have descriptions in the schema, achieving 100% coverage. The description does not add any additional parameter-specific semantics; it only mentions reportDate snapping indirectly through the description's mention of quarter-end dates, but that's already in the schema. With high schema coverage, the baseline of 3 is appropriate.

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's function: retrieving the top institutional buyers and sellers for a stock based on absolute share changes versus the prior 13F report. It uses a specific verb ('Get') and resource ('institutions'), and differentiates itself from related tools by emphasizing 'moved the needle the most' and the quarterly comparison. The purpose is unambiguous and distinct from siblings like GetInstitutionQuarterlyActivity or GetTopHolders.

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 provides explicit usage guidance with 'Use this to surface the most actionable quarterly signal from 13F filings,' and it explains when results may be incomplete (open filing window) and the handling of funds that stopped filing. However, it does not explicitly contrast with alternative tools or state when not to use it, so it stops short of full 5.

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