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

Beyond the annotations (readOnlyHint, idempotentHint, etc.), the description discloses the login requirement, default ordering, pagination cursor behavior, and the authorization restriction to conversations the user participates in. This adds meaningful behavioral context not present in the 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?

The description is compact, front-loaded with the login requirement, and uses two sentences to convey default behavior, pagination, incremental polling, and access restrictions. Every sentence earns its place.

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 read-only message retrieval tool with 4 parameters fully documented in the schema and safety annotations already present, the description sufficiently covers authentication, pagination semantics, ordering, and authorization. No critical information 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?

Although the schema already describes all four parameters at 100% coverage, the description adds important semantics: default returns recent messages in reverse order, after enables forward incremental polling, and nextBefore cursor supports backward paging. This goes beyond the raw schema descriptions.

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 clearly states the action '读取某个会话的消息' (read messages of a conversation) and adds the scope constraint '只能读自己参与的会话'. This distinguishes it from sibling tools like get_conversation or list_my_conversations by focusing on message content within a specific conversation.

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 explicitly explains the default behavior (recent messages, reverse order, nextBefore cursor) and when to use after=<messageId> for incremental polling. It provides clear usage context but does not explicitly name sibling alternatives or state when not to use this tool.

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