Update the deck settings

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

Annotations already flag destructiveHint=true and idempotentHint=true; the description adds the meaning behind them: this is a merge (partial update), not a wholesale replace, 'null deletes a key' is the destructive path, and comments/ordering survive. That is real added context. It stops short of saying whether unknown keys are rejected or whether the deck must be rebuilt afterward.

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 sentences, front-loaded with the verb and resource. The parenthetical key list earns most of its space by showing what 'settings' means, though it slightly duplicates the deck_reference pointer that follows it.

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 no explanation, and annotations cover safety. The description supplies the essential mutation semantics (merge, null-deletes, comment/order preservation). Missing only edge behavior: nested key handling and whether changes require deck_build to take effect.

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 50% — `dir` is documented in the schema, but `patch` is an untyped object with additionalProperties {} and no description. The description carries `patch` semantics itself: keys are merged, null deletes. It does not clarify merge depth for nested values, which matters given nested objects are present.

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?

Names a specific verb+resource (merge keys into headmatter) and defines the resource inline as the YAML block at the top of deck.mdx, listing example keys. It routes to deck_reference for the full key list rather than differentiating against other siblings, but an agent can tell this is a settings-mutation tool.

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 'configures the deck' — use it to change deck settings — and 'see deck_reference deck' points at where to find valid keys. There is no explicit when-to-use vs deck_create or deck_frontmatter_schema, and no statement of prerequisites or whether a rebuild is needed.

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