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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds real context beyond that: the tool returns routing URL, revision, and last update time, and it warns that reading a whole supergraph risks exceeding the model's token limit. It does not describe pagination or error behavior.

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?

Four tight sentences, front-loaded with what is returned, then the token-limit rationale, then the required inputs, then the discovery alternative. Every sentence carries information; none restates the name.

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 an output schema present, return-value explanation is not strictly needed, yet the description briefly notes the returned fields. It also names the three required params and the prerequisite discovery tool. The only gap is that the 0%-covered parameters get no format detail.

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 0%, so the description must carry parameter meaning. It enumerates the three required inputs in prose ('the graph ID, the variant name, and the subgraph name'), which maps them to the schema, but adds no format, casing, or valid-value guidance. It compensates only partially for the documentation gap.

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 one subgraph's published schema (SDL) from a variant') and enumerates the returned fields (routing URL, revision, last update time). It implicitly distinguishes itself from GetSupergraphSchema by warning that the whole supergraph document is much larger, so an agent can pick the right tool without opening the 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 a clear precondition-with-alternative: 'Use GetVariantDetails first if you do not know the subgraph names.' It also implicitly steers away from whole-supergraph reads via the token-limit note. It does not explicitly contrast with the sibling GetGraphSchema, so it falls short of a full when/when-not statement.

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