B站登录态与账号状态

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds the non-obvious behavioral fact that login state is not obtained by this tool and that an authenticated cookie must already exist, which is exactly the kind of context annotations cannot express. It does not discuss failure modes or caching, keeping it short of a 5.

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?

Two sentences, no filler, with the return-value enumeration front-loaded and the login caveat following. Every clause earns its place and there is no redundancy with the title or annotations.

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?

There is no output schema, so the description usefully enumerates the returned fields, and it explains the unauthenticated path via the login skill. For a zero-parameter read tool this is nearly complete; only minor detail (e.g., whether values are live vs cached, error shape when unauthenticated) 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?

The tool takes zero parameters, so the schema has nothing to misinterpret and the baseline for an argument-free tool applies. No parameter information is needed or missing.

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 names a specific verb+resource (读取当前 B 站登录态) and enumerates exactly what it returns: 昵称、UID、硬币、等级、未读通知/私信数. That is far more specific than the title alone. It stops short of explicitly distinguishing itself from siblings like user_info or notifications, so it is clear but not fully sibling-differentiated.

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 an explicit precondition and redirect: when not logged in, use the bilibili-login skill to inject the Cookie from the browser, and it states that the MCP itself does not perform login. That is a real when/when-not signal with a named alternative. It does not, however, say when to prefer this over user_info or notifications for overlapping data.

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