read_thread

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

With no annotations present, the description must carry the behavioral burden. It explicitly says 'Read-only,' which is a crucial safety signal, and it discloses a real limitation: not every post has a thread because a linked discussion group is required. It does not describe pagination, error responses, or whether nested replies are included, but those gaps are partially mitigated by the simple scope and the schema's limit parameter.

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 short sentences deliver the core definition, the two possible contexts, the linked-discussion prerequisite, and the read-only nature. There is no filler or redundant restatement of the tool name.

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 three-parameter read operation with a complete schema, the description covers the essential context: what is returned, where threads exist, and the read-only safety property. The lack of an output schema is partly offset by the phrase 'replies under one post,' though a bit more detail about response shape or limits would make it fully complete.

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%, so the baseline is 3. The description reinforces that message_id identifies 'the post' and that the tool returns 'replies under one post,' but it adds no parameter-specific meaning beyond what the schema already states.

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 precisely defines the resource: replies under a single post, with concrete examples of where such threads exist (channel comment sections or group reply chains). This clearly differentiates read_thread from siblings like read_chat or get_messages, which operate at chat or message-list granularity.

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 gives clear contextual guidance: this tool is for reading replies to one specific post, not general chat content. It also states a key precondition—only posts with a linked discussion group have a thread—which helps an agent decide when read_thread is applicable. It does not explicitly name alternatives or when-not-to-use cases, so it stops short of a 5.

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