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

Annotations already declare readOnly/idempotent/non-destructive/openWorld, so the description's value is in the extras it adds: the token-limit hazard of pulling a whole supergraph and the fact that responses include routing URL, revision, and last update time. It does not mention auth requirements or error modes, keeping it just short of a 5.

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?

Every sentence carries a distinct load — purpose, output contents, tool equivalence, scope warning, required inputs, prerequisite — and the purpose is front-loaded in the first clause.

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?

Output schema exists so return values need not be re-explained, and the description still covers scope, prerequisites, and the cost of the wrong call. Nothing an agent needs before invoking this read 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 0% and all three parameters are required but typed only as strings. The description restates their meaning ('Provide the graph ID, the variant name, and the subgraph name'), which maps names to concepts but adds no format, casing, or discovery guidance, so it partly compensates without fully doing so.

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 precise verb+resource ('Read one subgraph's published schema (SDL) from a variant') and enumerates the returned fields, which cleanly separates it from GetSupergraphSchema and GetGraphSchema among the siblings.

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 an explicit when-not ('Read one subgraph at a time: a whole supergraph document is much larger and can pass the token limit') and a fallback workflow ('Use GetVariantDetails first if you do not know the subgraph names'), plus the equivalence with `rover subgraph fetch` for readers who know that tool.

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