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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds value beyond that by disclosing the return shape ('full markdown body') and the mutation model of the related update tool (replace or append against current body), which matters because there is no output schema.

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 tight sentences, front-loaded with the core action and identifier source, followed by the one piece of workflow advice that actually changes agent behavior. No filler.

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?

With no output schema, the description correctly compensates by naming the return value ('full markdown body'), and it covers the edit relationship. What an agent needs to call it correctly is present; only deeper behavioral detail (e.g. permissions, missing-doc behavior) is absent.

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%, and docId's description already says it comes from napkin_docs_list, so the description largely repeats the schema on that point. It adds nothing about the workspace parameter, relying on the schema for the token/default-workspace rules, which is the expected baseline.

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 ('Fetch one Napkin doc's full markdown body') plus the identifier source ('by id (from napkin_docs_list)'). It distinguishes itself from the list tool that produces ids and the update tool that consumes the body, so an agent can route without opening 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?

Gives clear sequencing guidance ('Read before editing') and names the downstream alternative (napkin_docs_update) along with its semantics ('replaces or appends against the current body'). It lacks an explicit when-not condition, but the usage context is unambiguous.

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