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

Annotations already declare it is a non-read-only, non-destructive, closed-world write. The description adds genuinely new behavioral context beyond that: the header level is immutable after insert and editor_updateElement can only change isHidden, required, and titleIsHidden. That immutability constraint is exactly the kind of trait annotations cannot express.

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 with no filler. Purpose comes first, then the level scale, then the immutability caveat — a well front-loaded ordering that an agent can act on immediately.

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 7-parameter write tool with no output schema, the description covers the purpose, the level semantics, and the key post-insert constraint. It says nothing about what is returned (e.g., the new node ID) which matters for chaining with $prev/after, but the schema's 'Use $prev to chain' note largely compensates.

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%, so the baseline is 3, but the description adds meaning beyond the schema by clarifying that level 1 = largest and that 1-4 map to sizes. It also contextualizes which props updateElement supports later, tying back to isHidden/required/titleIsHidden semantics.

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 ('Insert a heading element'), which cleanly separates it from siblings like editor_insertParagraph or editor_insertList. It is clear about what is produced, though it never explicitly contrasts itself with the closest sibling (paragraph/rich-text insertion), so it stops short of a 5.

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 rather than stated: a reader infers this is for headings of level 1-4 versus body text elsewhere. There is no explicit when-to-use/when-not guidance or named alternative for the 'insert text block' decision, but it does give useful context on the level scale.

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