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

Annotations already carry the safety profile: readOnlyHint=false signals an append-style write, idempotentHint=true means re-labeling is safe, and destructiveHint=false means existing posts/labels are not destroyed. The description's 'Add a label/tag' wording is consistent with these annotations but adds minimal behavioral context beyond them (only the 'saved posts' scoping). No contradiction exists; the description simply doesn't enrich beyond what annotations convey.

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 zero waste. The primary action is front-loaded in the first sentence, and the second sentence earns its place by giving actionable workflow guidance. Nothing is redundant or decorative.

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 simple, low-risk write tool with only two fully documented parameters and annotations covering idempotency and destructiveness, the description is nearly sufficient. It covers purpose and prerequisite workflow. Minor gaps remain — no mention of what happens with invalid post IDs, whether new labels are auto-created, or return format — but these are low-stakes for this use case.

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% — both label ('The label to add') and post_ids ('Array of post IDs to label') are already documented in the schema. The description mirrors these concepts ('post IDs', 'label') without adding format, length, or edge-case semantics. Per rubric, high coverage warrants baseline 3.

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 ('Add'), a concrete resource ('label/tag'), and the object being modified ('one or more saved posts'). This action is unambiguous and clearly distinct from siblings like remove_label, list_labels, and add_note without needing to open any schema.

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 workflow context: 'Search first to get post IDs, then label them.' This tells an agent the prerequisite step and when the tool fits in a sequence. However, it does not explicitly name alternatives or state when-not-to-use conditions, so it stops short of a full 5.

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