begin_design

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

Annotations already cover the safety profile (readOnly=false, idempotent=true, destructive=false), and the description adds genuinely new behavior beyond them: it pins and hash-verifies the packaged macro registry, and notes that oversized optional receipt fields may be omitted via truncated:true after commit. These are real operational traits, not restatements of annotations.

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?

The core action is front-loaded in the first sentence and the sentences are dense and mostly earn their place. The trailing truncated:true/receipt-fields sentence is somewhat opaque and references concepts not present in the input schema, slightly diluting clarity.

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 4-param creation tool with nested objects and no output schema, the description covers the mutation behavior, idempotency, and persistence well, but never indicates what the call returns (e.g. the created session or registry pin), which an agent would need in the absence of an output schema.

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 the schema already documents all four parameters well. The description lists the parameters and lightly clarifies profile ("alias or ref"), but adds little syntax or semantics beyond the schema's own descriptions. Baseline 3 is appropriate.

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?

The description opens with a specific verb+resource ("Create a persistent design session") and adds a scope detail ("under the host project root"), clearly separating it from siblings like apply_design_patch or validate_design. It is clear, though it never names a sibling explicitly for disambiguation.

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 implied rather than stated: an agent infers this is the entry point that starts a session before patching/validating. "Idempotent for the same operationId" hints at safe re-invocation, but there is no explicit when-to-use/when-not guidance or named alternative.

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