PDF: margin note or reply

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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the write/safety profile is covered. The description adds one genuine behavioral fact — the 'save-Okular-first' caveat — but only by deferring to mark_text, so the agent must already know that sibling to act on it.

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?

Three tight sentences, front-loaded with the two modes and back-loading the anchor elaboration. Dense and waste-free, though the backtick-heavy cross-references cost some readability.

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?

Output schema exists so return values need no explanation, and the annotation set covers safety. But for a non-idempotent mutation with 6 undocumented parameters, the description omits whether near_text and reply_to are mutually exclusive and what happens to page/path defaults.

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% across 6 parameters, so the schema gives no semantics. The description compensates for three of them (near_text, reply_to, color) with clear roles, but leaves note, page, and path entirely unexplained, including which anchor fields are mutually exclusive.

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 action (place a comment icon / reply to an annotation) on a specific resource, and explicitly splits the tool into two modes: a margin note anchored via near_text, or a threaded reply via reply_to. An agent can distinguish it from mark_text and annotations by the named anchors alone.

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 gives selection logic for the anchor: use near_text for a margin-level icon, reply_to (an xref from annotations) to answer an existing note, otherwise it falls back to the top of the page. It names sibling tools but never states the when-not condition versus mark_text, which is the closest alternative.

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