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

The annotations already flag readOnlyHint=false and destructiveHint=true, so the agent knows this mutates state. The description adds genuinely useful non-annotation context ('Cost: Free') and clarifies that marking is done via a reply, but it never says what the destructive effect actually is, whether an existing reply is overwritten, or whether the change can be undone. The opening word 'Lists' mildly understates that this is a write-capable tool.

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 short clauses with the read behavior front-loaded and the write behavior second; nothing is redundant. The 'Cost: Free' tag is terse but reads as an appended billing note rather than integrated information, and 'with its reply' is compressed to the point of ambiguity.

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 described, and all parameters are covered by the schema. However, for a zero-required-parameter tool that polymorphs between listing and mutating, the description omits the trigger condition and the consequences of the destructive mark, which is a real completeness gap.

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 all five parameters are already documented, and the schema even states that the open video is used when video_id is omitted. The description's 'with its reply' loosely ties the reply parameter to the marking action, but adds no format, length, or mutual-dependency semantics beyond the schema. Baseline 3 applies.

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 names two concrete operations on a specific resource: listing a video's pinned notes and marking a note working or done. That is far more informative than the bare name 'project_notes'. It stops short of distinguishing itself from the sibling 'finish_working', which sounds like it covers overlapping territory.

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?

There is no explicit when-to-use guidance and no mention of alternatives or exclusions, even though 'finish_working' exists as a plausible sibling for the status-change half. The description also never states that supplying note_id/status switches the tool from listing to mutating, which is the key usage decision an agent faces.

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