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

Annotations already cover the safety profile (readOnly/idempotent/non-destructive), and the description adds substantial context beyond them: Free returns 5 with an `items_note` truncation signal, Pro up to 25, routine filings are suppressed for all tiers, filings lacking usable text have no summary, and recording happens only pre-open and post-close so recent filings may be missing. It even disambiguates `sentiment` as news tone rather than a price call.

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?

Front-loaded with purpose, then tiering, then field semantics, then coverage and alternatives — a logical order with bulleted structure. It is slightly over-long because it enumerates every returned field even though an output schema exists, making part of that list redundant.

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 an output schema and full annotation coverage, the description fills the remaining gaps an agent needs: tier-dependent result counts, universe restrictions, ingestion latency, suppression of routine filings, and the sibling to use for a combined timeline. Nothing material is left implicit.

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 coverage is 100%, so the baseline is 3. The description adds marginal value by explaining the practical consequence of `limit` — the tier caps and the `items_note` flag that appears when more filings exist than were returned — which is not in the schema itself.

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+scope: 'latest SEC 8-K filings of one company, newest first,' and defines what an 8-K is. It is clearly distinguishable from siblings like get_stock_news and get_stock_activity, which are named as different cuts of related data.

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?

Explicitly routes the agent: 'For the filing together with news, insider and analyst activity in one timeline, use get_stock_activity.' It also states eligibility boundaries (US-listed, USD, ~$1B+ market cap) and freshness caveats, so an agent knows when this tool will and will not return data.

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