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

Annotations (readOnlyHint=true, openWorldHint=false) already establish the safety profile, so the description's job is to add output expectations. It does: the result is 'a labeled starting point keyed by layer', explicitly not validated, which correctly sets the agent's trust level in the artifact. It does not mention determinism, size, or failure behavior for malformed package names.

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 sentences, no filler, with the concrete output named first and the caveats trailing. Every clause carries information an agent would otherwise have to guess.

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?

For a single-optional-parameter, read-only emit tool with no output schema, the description covers what is produced (a Mermaid diagram), the input expectation (already-chosen package names), and the trust caveat (starting point, not validated). Nothing critical is missing, though the shape/granularity of the emitted diagram remains unspecified.

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 100% and the single 'stack' parameter is fully described in the schema, including the omit/empty behavior, so the baseline is 3. The description only echoes '(package names)' without adding format, ordering, or layer-mapping semantics beyond the schema.

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 (Emit), a specific artifact (reference-architecture Mermaid diagram), and the input basis (a stack you have already chosen). It also draws a boundary against a plausible neighbor (an architecture designer), so an agent can tell it apart from design/validation tools.

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 the precondition for use ('a stack you have already chosen') and explicit exclusions ('not a validated architecture, and not an architecture designer'), which tells the agent when this is the wrong tool. It never names an alternative sibling to use instead, so it stops short of a full when/when-not/alternative statement.

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