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

Annotations already cover read-only and non-destructive behavior. The description adds valuable context: that comparisons happen on the latest common report date, that filer names resolve via SearchInstitutions, and what metrics are returned. This goes beyond annotations but doesn't fully detail pagination or maxResults behavior, though those are in the schema.

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?

Two sentences pack the core purpose, output, and usage guidance with zero waste. The primary action is front-loaded, and the alternative tool is mentioned at the end in a natural place.

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 description clearly states what the tool returns (Jaccard and dollar-weighted overlap, totals, shared/unique positions), which is essential given no output schema. It also points to SearchInstitutions for name resolution and GetFundProfile for NPORT portfolios. Missing details like maxResults clamping are covered in the schema, so overall it's sufficiently complete.

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 fully documents all four parameters (including name resolution and date snapping). The description doesn't add new parameter-level meaning beyond what's in the schema, so baseline 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 specific action (compare two institutions' 13F portfolios), the timing (latest common report date), and the specific outputs (Jaccard and dollar-weighted overlap, portfolio totals, shared/unique positions). This distinguishes it from siblings like GetInstitutionPortfolio (single institution) and GetFundProfile (mutual funds/ETFs).

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 states when to use an alternative: 'For mutual-fund or ETF NPORT portfolios, use GetFundProfile' and tells users to resolve filer names via SearchInstitutions. This gives clear when-to-use and when-not-to-use guidance beyond the inherent 'compare two' purpose.

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