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

The annotations already declare idempotentHint=true and destructiveHint=true; the description corroborates both ('one note per date (re-adding replaces it)') and explains what 'destructive' means here, which is real added value. It also discloses quota impact ('each counts as one data point'), which no annotation covers. It stops short of saying what happens to markers on an existing date's text or whether the write is reversible.

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?

One sentence, front-loaded with purpose, followed by a parenthetical example and a semicolon-separated constraint list. Every clause carries new information; nothing is padding.

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 only two required parameters, no output schema, and annotations already covering the safety profile, the description supplies everything needed to call correctly: the annotation object shape in practice, text limits, uniqueness per date, and the data-point cost. No material gap remains for an agent making the call.

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 coverage is 100%, but the schema leaves 'annotations' as an untyped array of generic objects with only a raw example. The description compensates with real constraints the schema lacks: single-line plain text, 280-character cap, one note per date, and replacement semantics on re-add.

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 states a specific verb and resource ('Attach short dated notes to a series') and adds the observable effect ('shown as markers on charts'), which clearly separates it from list_annotations and delete_annotations. The parenthetical example makes the object of the operation concrete.

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?

Usage is implied by the verb and the example, but the description never explicitly says when to add annotations versus listing or deleting them, nor does it name any sibling tool. An agent can infer the intent but must reason about it rather than being told.

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