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

Annotations already declare the operation is mutating but non-destructive and closed-world, so the safety bar is lower. The description adds that slides are appended to an existing deck (position at end) and how content maps to layout text areas, which is useful behavioral context beyond the annotations.

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 sentences, front-loaded with the purpose, and the ordering instruction comes last. The inline layout enumeration duplicates the schema's layout description verbatim, which is minor redundancy, though the enumeration does earn its place as an at-a-glance reference.

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 moderate-complexity, 5-parameter mutation tool with no output schema, the description covers purpose, layout choice, content formatting, and a prerequisite check. It does not describe what is returned (e.g., a slide id usable with napkin_slide_update), but with no output schema that omission is acceptable.

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 real meaning beyond it: content is 'markdown for the layout's remaining text areas' and 'two-column/comparison take one block per column.' It explains the per-column block behavior that the schema does not.

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 verb and resource: 'Appends one slide to an existing deck.' An agent can tell this adds a single slide rather than creating a deck. However, it never explicitly distinguishes itself from siblings like napkin_deck_write, napkin_slide_update, or napkin_slide_fill, so differentiation is left to inference.

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?

Gives a concrete workflow prerequisite: 'Check the deck first with napkin_deck_outline,' naming a companion tool. It also clarifies what to supply (layout, title, optional content). It stops short of explicit when-not-to-use guidance or naming the write/update siblings as alternatives.

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