chat_message_send

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

With no annotations provided, the description carries full burden. It discloses key behaviors: reconstructs conversation history, stores both user and assistant messages, and returns token usage. However, it doesn't mention rate limits, authentication requirements, error conditions, or whether this is a read-only or mutating operation.

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 perfectly concise with two sentences that each earn their place. The first sentence states the core action and context, while the second explains key implementation details and return values. No wasted words or redundant information.

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 tool with 3 parameters, 100% schema coverage, but no annotations and no output schema, the description is adequate but has gaps. It explains the core functionality well but doesn't address error handling, authentication, or provide examples of the return format beyond mentioning 'assistant reply with token usage'.

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 already documents all three parameters thoroughly. The description adds minimal value beyond what's in the schema - it mentions 'message content' which aligns with the content parameter, but doesn't provide additional context about parameter interactions or usage patterns.

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 specific action ('Send a message'), the resource ('in an existing session'), and the outcome ('get a Claude response'). It distinguishes from siblings like chat_session_create (creates new sessions) and chat_message_list (lists messages) by focusing on message sending within existing sessions.

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 implies usage context by specifying 'in an existing session' and mentioning conversation history reconstruction, which suggests this is for ongoing conversations rather than starting new ones. However, it doesn't explicitly state when NOT to use this tool or name alternatives like chat_session_create for new conversations.

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