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

Annotations already indicate readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds key behavioral details: for company type it pulls financial data from SEC EDGAR/XBRL with off-calendar year handling, for drug type it pulls FAERS and FDA data. It also mentions results are sorted by primary metric and returns citation URIs. No contradiction with 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?

The description is a single paragraph but effectively structured: starting with user query examples, then stating purpose, then detailing type-specific behavior. It's slightly long but every sentence adds value. Could be slightly more concise but still very good.

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 the tool's complexity (two entity types, financial and drug data, sorting, citation URIs), the description covers essential aspects. It mentions return format (paired data + URIs) but doesn't detail exact output structure. However, annotations and schema compensate. A brief note on rate limits or pagination would improve completeness.

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% but the description adds significant value: it provides example inputs (e.g., 'AAPL','MSFT'), explains what each type does, and clarifies constraints (2-5 values). This goes well beyond the schema's brief descriptions.

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 explicit user queries ('Compare X and Y', 'X vs Y', 'which is bigger') and states the tool provides side-by-side comparison of 2-5 companies or drugs. It clearly distinguishes itself from sequential lookups by saying 'ALWAYS PREFER over sequential single-pack lookups'. The verb 'compare' and resource 'entities' are unambiguous.

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 prefer this tool over sequential lookups when comparing entities. It also explains what each type returns (company vs drug). It doesn't explicitly state when not to use it, but the context is clear.

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