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

The description goes beyond the readOnlyHint annotation by disclosing operational nuances: published values normally use report-date closing prices, may fall back to filer values, and can be zero when unavailable. This is material behavioral context that an agent needs to interpret results correctly.

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?

Four sentences, each carrying distinct value: what the tool does, what it returns, how to interpret data caveats, and which sibling to use instead. The most important information is front-loaded and there is no filler or repetition of schema content.

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?

Despite having no output schema and minimal annotations, the description covers purpose, return values, data caveats, name resolution, and the key alternative tool. For a read-only comparison tool with four well-documented parameters, this is sufficient for an agent to select and invoke it correctly.

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 schema already fully documents all four parameters. The description adds some context about the 'latest common report date' and the fact that inputs are institution names, but it does not materially enrich parameter understanding beyond the schema. 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 starts with a strong verb and resource: 'Compare two institutions' 13F portfolios' and specifies the exact output: Jaccard and dollar-weighted overlap, portfolio totals, and shared or unique positions. It also distinguishes itself from GetFundProfile for NPORT portfolios, making it clear what the tool is not for.

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 explicitly says to use SearchInstitutions for resolving filer names and to use GetFundProfile for mutual-fund or ETF NPORT portfolios instead. This gives clear routing guidance and tells the agent when this tool is appropriate versus when an alternative should be chosen.

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