add_marker

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

There are no annotations, so the description carries the behavioral disclosure burden. It transparently communicates that this is a mutating operation and adds the useful non-active-sequence nuance. However, it does not mention return behavior, idempotency, or what happens to existing markers at the same time.

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?

Two sentences with no filler. The main action is front-loaded, and the important non-active-sequence exception is stated in a short second sentence. Every word 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?

For a straightforward additive operation with a fully described schema, the description is adequate. The main gap is the absence of return-value or error information, but the tool's purpose and parameters are clear enough for an agent to invoke it correctly.

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 input schema already documents all six parameters. The description adds general purpose context but no parameter-level detail beyond what the schema provides, which matches the baseline for full schema coverage.

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 ('Adds a marker') and the target resource ('the specified sequence'), with a purpose ('for navigation or notes'). It also distinguishes itself from active-sequence-only operations by noting the sequence does not have to be active, which separates it from many sibling timeline tools.

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 provides clear usage context: markers are for navigation or notes, and the tool works on non-active sequences. It does not explicitly name alternatives like update_marker or place_markers, so it stops short of full alternative-routing guidance.

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