mcpmessage_thread

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds meaningful context beyond that: it accepts both root and reply ids, returns messages in order, and returns an 'Error: ...' string when the message does not exist. This is useful behavioral detail without contradicting 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 concise and well-structured: a one-sentence summary, a short explanatory sentence, then explicit Args and Returns sections. Every part earns its place and the most important semantic points are front-loaded.

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 one-parameter read-only tool with strong annotations, this is complete. It covers what the tool returns, the shape of the response, the accepted input, and the error case. No additional information is needed for an agent to invoke it correctly.

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, and it does thoroughly. It explains that message_id can be any message id in the thread, including the root send or any reply, which adds real meaning beyond the bare parameter title 'Message Id'.

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 opens with a precise verb and resource: 'Return the full thread a message belongs to, in order.' It also clarifies that any message id in the thread works, which clearly distinguishes this from sending, listing chats, or checking an inbox. The purpose is unambiguous.

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 explains exactly when to use the tool: to follow a conversation across replies by passing any message id from the thread. It does not explicitly name alternatives or exclusions, but the context is clear enough that an agent would not confuse this with siblings like mcpmessage_send or mcpmessage_inbox.

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