append

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

Annotations declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the safety profile is already known; the description still adds meaningful behavior beyond them: retries with the same event_id are deduplicated, and reasoning content must not be recorded. It stops short of stating permissions or what the append returns.

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?

Four short sentences, purpose front-loaded, each carrying a distinct rule (idempotency, origin wiring, reasoning prohibition). No filler, though the origin sentence is dense and could be split.

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?

With a 5-parameter schema including a nested object, no output schema and zero schema descriptions, the definition covers the critical fields but omits the meaning of the kind enum and the date format, leaving an agent to guess on a required parameter.

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 carry parameter meaning. It does explain the semantics of event_id (idempotency key) and three of the four nested origin subfields (project, session, agent), but leaves kind's enum values, text, date and origin.machine unexplained.

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+resource: 'Record one message of the chat.' An agent can tell this is the write/append path versus read-only siblings like view, search, thread and read_message. It doesn't explicitly name those siblings, keeping it below a 5.

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?

Gives clear operating context plus an explicit exclusion ('Never record reasoning') and idempotency guidance ('A retry with the same event_id adds no copy'), which tells the agent it may safely retry. No explicit pointer to an alternative tool, so not a 5.

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