express_read_thread

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

With no annotations at all, the description carries the full burden and does disclose the non-obvious side effect: opening the parent chat marks it read and navigates into the thread. That is exactly the kind of consequence an agent cannot infer. It stops short of describing pagination behavior for the unexposed 'limit' parameter or what the attachment metadata contains.

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, front-loaded with the operation and identifiers, with the destructive side effect isolated in a clearly marked WARNING. No filler or 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?

There is no output schema and no annotations, yet the description covers the call inputs, the ID source, and the important side effect, which is enough for an agent to invoke it correctly. The only real gap is the undocumented 'limit' parameter and any note on reply volume or ordering.

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 0%, so the description must compensate: it explains chatId and threadId including their provenance, which is genuinely useful. However the third parameter, 'limit', is never mentioned in either the schema or the description, leaving its semantics and default unknown.

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 and resource ('Read a thread's replies') and pins the two identifiers, chatId + threadId, so it is distinguishable from express_read_chat and express_list_threads. It even names where the IDs come from, which removes any ambiguity about what entity is being read.

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 clearly implies the precondition ('from express_list_threads'), telling the agent to enumerate threads before reading one, and the WARNING frames the cost of calling it. It never explicitly contrasts with express_read_chat for reading the parent chat itself, so the when-not guidance is only partial.

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