Holders

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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered; the description adds real value beyond them by disclosing the equity-only failure mode and the exact composition of the response. It omits any note on data freshness/delay, which is the main remaining behavioral gap for a market-data read.

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?

Three short sentences, front-loaded with purpose, then return contents, then the constraint. No filler and nothing redundant with the schema.

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 an output schema present, return values need no explanation, and the description still covers the one gotcha an agent would hit (non-equity symbols erroring). It is nearly complete, lacking only peripheral context such as data recency.

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 both 'symbol' (ticker/ISIN format plus the 'use search first' hint) and 'limit' (per-list cap) are fully documented in the schema. The description adds no syntax or format detail beyond that, so the baseline 3 applies.

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?

States a specific verb+resource ('Get the ownership breakdown for a Yahoo symbol') and enumerates exactly what comes back: insider/institutional percentages plus top institutional and mutual-fund holders. The equity-only clause implicitly separates it from get_fund_data and get_insider_activity, so an agent can distinguish it from siblings without opening a schema.

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?

Gives a clear when-not rule: ETF, fund or crypto symbols return an error saying so, which prevents wasted calls on non-equity tickers. It does not name alternatives (e.g. get_fund_data for funds, get_insider_activity for transaction-level detail), so routing guidance 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.