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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds information they cannot carry: 'Charges nothing' (no credit cost) and 'Requires OAuth or an API key' (auth prerequisite). It does not cover failure behavior for an unauthenticated or expired credential, which is the main remaining behavioral gap.

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?

Front-loads what is returned, then when to call it, then the cost and auth facts — in three sentences with no filler or repetition. Every sentence contributes distinct information.

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 no output schema, the description compensates by enumerating the returned fields and the credit-balance breakdown, and it states the auth requirement and zero cost. Nothing an agent needs to decide to call this 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?

The tool takes zero parameters, so the baseline is 4; there is nothing for the description to disambiguate and it correctly says nothing about inputs beyond the auth requirement.

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 ('Returns the signed-in Open-End account') and enumerates the returned payload: username, e-mail, credit balance broken down into balance/reserved/available, plus credential scopes. That enumeration makes it clearly distinct from siblings like open_end_get_project or open_end_get_capabilities without needing to name them.

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 three concrete triggering scenarios: 'how many credits do I have', checking before suggesting a paid analysis, and verifying which account the connector is signed in to. That is strong positive guidance, though it stops short of naming an alternative tool or stating any when-not-to-use condition.

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