upsert_message_into_timeline

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

With no annotations, the description carries the full burden of disclosing behavioral traits. It mentions the internal pipeline (extract, merge, recompute) but does not clarify whether the input existing_timeline_state is mutated, whether the operation is idempotent, what the return value is, or how duplicate messages are handled. This is a significant gap for an upsert-style 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 a single sentence with no wasted words. It front-loads the primary purpose and quickly conveys the key operations, making it easy to scan and parse.

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?

Given the tool's moderate complexity (nested objects, 2 required params, no annotations, no output schema), the description is not complete enough. It omits critical details such as the expected shape of existing_timeline_state, whether the updated state is returned, and how errors or duplicates are handled. An agent would struggle to invoke this tool correctly without additional information.

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 compensate for the schema's lack of parameter details. It does not: it only refers to 'one new message' and 'existing state' without explaining the structure of existing_timeline_state, how message.id/text/timestamp are used, or any constraints. The description adds minimal semantic value beyond the parameter names.

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 action: 'Incrementally update a running timeline with one new message,' and outlines the sub-steps of extracting events, merging, and recomputing derived fields. It implicitly distinguishes from build_timeline_state by focusing on incremental update, but it does not explicitly name or contrast with siblings.

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 when to use the tool: when there is a new message to add to an existing timeline state. However, it does not explicitly state when not to use it or mention alternatives like extract_timeline_events or build_timeline_state, so the guidance is only implied rather than directly actionable.

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