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

Annotations already indicate this is not read-only, is idempotent, and is not destructive. The description adds meaningful behavioral context: 'You are walked over to stand with that group; your next `say` goes to them.' This explains the state change and the effect on subsequent actions, going beyond 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?

Two sentences, front-loaded with the purpose, and no filler. The second sentence earns its place by explaining an important behavioral consequence. Well-structured for quick agent parsing.

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, two-parameter tool with annotations and full schema coverage, this description is complete. It tells the agent what the tool does, where the id comes from, and what happens after joining. No critical information needed for correct invocation is missing.

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 schema fully documents both room and conversationId. The description slightly reinforces that conversationId comes from list_conversations and clarifies the social effect, but it does not add substantial parameter meaning beyond the schema. Baseline 3 is appropriate.

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 specific verb and resource: 'Join an existing conversation by id'. It also names the source (list_conversations), which distinguishes this from start_conversation and read_conversation. The behavior is clearly differentiated from sibling tools.

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 provides clear context: use it to join an existing conversation identified by an id from list_conversations. It does not explicitly list when-not-to-use or name start_conversation as the alternative for creating a new conversation, but the word 'existing' implies that boundary. This is strong but not fully explicit.

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