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

Annotations declare a non-read-only, non-idempotent, open-world operation, and the description adds meaningfully beyond them: it requires the api:account scope, returns a portal URL rather than completing the connection, and hands off to a human browser flow plus polling. That auth and out-of-band completion detail is exactly the context annotations cannot 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 action and return value, then the required human workflow, then the optional-param behavior. Every sentence earns its place with no filler.

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 single-optional-param tool with no output schema, the description supplies the missing pieces: what it returns (a URL), that the connection is not completed synchronously, the scope needed, and the polling follow-up. Nothing an agent needs to invoke it correctly is absent.

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%, so the description carries the param burden, and it does: broker is a SnapTrade slug (with ROBINHOOD as an example), it is optional, and omitting it lets the user choose. Only the maxLength/minLength constraint and the full slug vocabulary remain undocumented.

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 ('Start a SnapTrade connection for YOUR account') and immediately names the return value (a portal URL), so an agent can distinguish it from sibling setup tools like get_setup_status and list_brokerages without opening any 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?

It gives the exact follow-up workflow: show the URL to the user, have them finish login in the browser, then poll get_setup_status until brokerage_connected is true. It also explains when to omit the broker param. It stops short of explicit when-not-to-use or prerequisite ordering against other siblings, but the routing context is strong.

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