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

Annotations already declare readOnly/idempotent/openWorld. The description adds meaningful context about data sources (CURRENT vs HISTORIC disclosure files) and the ranking logic behind market-wide results, which annotations cannot convey. Doesn't cover return shape, but nothing contradicts 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?

Front-loaded with the definition, followed by filter semantics and two concrete examples. Dense but each sentence earns its place; the double example is slightly more than strictly needed but aids invocation.

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?

Covers what the tool does, how filters interact, and examples of correct invocation. Without an output schema, the description could be more explicit about the shape of returned deltas, but for a read-only tool with well-documented parameters this is largely sufficient.

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 already 100%, so baseline is 3; the description adds value by explaining the interaction between parameters – specifically that omitting issuer/ISIN triggers largest-move ranking, and describing the 'since' date semantics vs current position date. Slightly redundant with schema but the interaction rules are useful.

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: per-issuer short-position deltas, and precisely defines what 'delta' means (latest CURRENT disclosed position vs most recent prior HISTORIC value). This clearly distinguishes it from siblings like fca_short_positions and fca_largest_shorts.

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 gives the two usage modes: filter to one issuer/ISIN, or omit both to get largest market-wide moves (optionally since a date). Worked examples with real parameter combinations make the routing unambiguous.

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