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

Annotations already declare readOnly, idempotent, closed-world, non-destructive, so the safety profile is covered. The description adds real behavioral value beyond that: it explains the result shape (each match with its source, kev/nvd nodes for CVEs, a uid usable with graph_node/graph_neighbors) and defines the empty-items case as 'no such id' rather than an error.

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 tightly packed sentences: the lookup rule and examples come first, followed by the return semantics and the empty-result edge case. No filler, and every clause carries information an agent needs.

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?

There is no output schema, so the description must carry return semantics — and it does explain match structure, source nodes, the uid chaining into graph_node/graph_neighbors, and the empty-list meaning. The label filter is left entirely to the schema, which is a minor gap given the otherwise strong coverage.

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% — both the id format (case-insensitive, no prefixes) and the label semantics (valid labels from graph_meta, unknown labels refused) are fully documented in the schema. The description adds no parameter meaning beyond what the schema already states, so the baseline of 3 applies.

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 ('Find nodes by exact external id') and grounds it with three concrete id examples (CVE-2021-44228, T1059.001, CWE-79). It does not itself differentiate from siblings like graph_search or graph_node, though that distinction lives in the schema rather than the description.

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 only implied by the word 'exact' — the reader infers this is not for prefix/free-text lookups, but the explicit 'use graph_search for a prefix' routing lives in the schema's id description, not the tool description. The empty-result note is helpful context but is not when-to-use guidance.

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