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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so the safety profile is covered; the description adds the return shape (path plus value, or items/total/offset/limit/nextOffset for list sections), which matters because there is no output schema. It does not say what happens for an invalid path (empty result vs error), which is the remaining gap.

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?

Front-loaded with the core definition, then usage routing, then return shape, then examples. The section enumeration is dense but functional; no wasted sentences.

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 and only three simple parameters, the description supplies everything needed: valid path roots, sibling routing, and the response envelope including pagination fields. Nothing an agent needs to call it correctly is missing.

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%, so path/limit/offset are already documented with defaults and bounds; the description only reiterates that limit/offset apply to list sections. The dotted-path examples add minor value but largely duplicate the schema's own examples.

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: 'Read-only fetch of one exact section or record by dotted path', and enumerates the valid top-level sections. An agent can distinguish this from nebula_list/nebula_search/nebula_overview 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?

Explicit routing: 'Use when you know the path from search/list', with each sibling named and its role stated (overview = summary, search = find paths, list = browse titles). Both the when and the when-not are covered.

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