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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuinely non-structured context by disclosing an auth prerequisite ('Needs a free StartupHub.ai account'), which is exactly the kind of behavioral context annotations can't express.

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?

Three tight sentences, front-loaded with the purpose, then the differentiation, then the use case and prerequisite. Every sentence carries distinct information with no repetition.

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?

For a simple one-parameter read tool with annotations covering safety, the description supplies purpose, sibling differentiation, the use trigger, the auth prerequisite, and a hint at the return content ('fund profile / portfolio info'). It stops short of mentioning there is no output schema, but nothing needed to invoke it correctly is missing.

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 0% for the single 'domain' parameter, so the description must carry the load, and it does identify the value as the fund's *website* domain (disambiguating from social handles, which has its own sibling tool). It does not specify format details such as protocol, www, or paths, keeping it below a 5.

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 and resource ('look up a single investor (VC, angel, accelerator) by their website domain') and explicitly distinguishes itself from the near-named sibling get_startup_by_domain ('against the investors table'). An agent can tell it apart from search_investors and get_startup_by_domain without opening a schema.

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?

Gives a clear when-to-use trigger: 'Useful when you have a fund's website and want fund profile / portfolio info.' It implies the single-lookup vs. search_investors split but doesn't state exclusions or name the alternative explicitly, so it stops short of a full routing rule.

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