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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds non-obvious behavioral context: accounts are optional for market tools, and consumers should default to the is_default flag — information an agent could not infer from the structured fields.

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 short sentences, front-loaded with the purpose and returned fields. Minor ambiguity: 'default_account_id' is referenced but not listed among the returned fields, leaving a small dangling reference.

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?

With zero parameters, no output schema, and rich annotations, the description carries exactly what is needed: what it returns, when it is unnecessary, and how to choose among multiple accounts. No pagination or filtering concerns apply.

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?

The tool takes zero parameters, so there is no parameter semantics to convey — baseline 4 applies. The description instead enumerates the returned fields (id, provider, balance, is_default), which usefully pre-frames the response even without an output schema.

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?

Specific verb+resource ('List all connected trading accounts') followed by the exact fields returned in parentheses. Nothing could be confused with the market/news/alert siblings, and the scope (all accounts) is explicit.

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 tells the agent when this tool is NOT needed ('Market tools work with zero accounts') and how to pick among results ('use is_default / default_account_id unless the user picks one'). It stops short of naming an explicit alternative sibling or exclusions, but the conditional guidance is clear.

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