matrix_send_message

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

With no annotations, the description carries the full burden and does well on the risky parts: dry_run is explicitly non-sending, and idempotency_key is disclosed as being forwarded as the Matrix transaction ID with duplicate-suppression semantics on retry. It omits permission/membership requirements and rate-limit behavior, so it is not complete, but the mutation-safety disclosure is above average.

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?

Three tight sentences, no filler, with the core action stated first and the two behavioral caveats following in order of likely relevance. Every sentence earns its place.

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?

An output schema exists, so return values need not be explained, and the description adequately covers the send/preview/retry paths of a mutation tool. It falls short on the unexplained tenant parameter and the complete absence of permission or membership preconditions expected for a room-scoped write.

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% across 5 parameters, so the description must compensate. It meaningfully explains body (plaintext content), dry_run, and idempotency_key, but leaves room_id and especially tenant completely undefined — the agent cannot tell what tenant scoping does or what value to pass.

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?

States a specific verb and resource ("Send a plaintext message to a room"), and the word "plaintext" implicitly distinguishes it from matrix_send_file and matrix_send_reaction. An agent can identify the correct sibling without opening any schema.

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 gives conditional guidance for two parameters (dry_run for previewing, idempotency_key for retries), which is genuine usage context. However, it never states when to prefer this tool over matrix_send_file for attachments or matrix_send_reaction, nor any prerequisite such as room membership.

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