send_message

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

With no annotations, the description carries the full burden. It does disclose the message-sending behavior, the return type (confirmation string), and the side-effect of creating a thread when using thread_key. However, it omits permission requirements, failure behavior, rate limits, and what happens if the space is invalid—details expected for a mutation tool with no 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 short, front-loaded with the core action, and uses a clear Args/Returns structure with no filler. It loses a point because the Args section is incomplete (only two of five parameters are listed), which could mislead an agent into thinking those are the only relevant inputs.

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?

Despite having an output schema for the return value, the description is incomplete for a 5-parameter tool with zero schema coverage and no annotations. It fails to explain the three required parameters, provides no cross-references to list_spaces or get_messages for finding a space_id, and does not mention authentication context. An agent would struggle to invoke this tool correctly based on this definition alone.

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 explain all parameters. It only explains thread_name and thread_key, and leaves the three required parameters (user_google_email, space_id, message_text) completely undefined. An agent cannot reliably infer what values to provide for these required fields from the description alone.

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 'Sends a message to a Google Chat space,' which states a specific verb and resource. It clearly distinguishes this tool from Gmail-related senders and Google Chat read/reaction tools. The reply behavior via thread_name/thread_key adds precision.

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 offers some in-tool guidance by explaining when to use thread_name vs thread_key, including the side-effect that thread_key creates a thread if not found. However, it gives no guidance on when to use send_message instead of sibling tools like create_reaction or get_messages, and no explicit exclusions or alternative routing.

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