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

Annotations already mark the tool as readOnly and openWorld, so the safety profile is covered. The description adds useful behavioral context by stating it returns /auth (Supabase Continue with X) and /x (tweet.write) links, but it does not clarify whether the connection persists, whether a subsequent call is required to actually post, or what happens if no authCode is provided. 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?

A single, front-loaded sentence states the action, the purpose, and the return values with zero filler. Every clause contributes to the agent's understanding of what this tool does.

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 read-only tool with one optional, fully documented parameter and no output schema, the description supplies the essential return information (/auth and /x links) and the context (connecting for posting). It could be slightly more complete by explaining the follow-up flow, but nothing critical is missing for correct invocation.

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 100%, and the authCode parameter already carries a detailed explanation of the auth contract. The tool description itself adds no parameter-level meaning beyond the schema, so the baseline of 3 is appropriate.

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 uses a specific verb ('Connect') with a clear resource ('the user's X account') and states the intended outcome ('so this MCP can post'). It is not a tautology and is instantly understandable, though it does not explicitly differentiate itself from sibling tools like x_link_start or x_link_verify.

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 implies this is a prerequisite for posting via the MCP, but gives no explicit when-to-use or when-not-to-use guidance, nor does it name alternative tools. An agent would have to infer the appropriate context from the tool name and surrounding sibling names.

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