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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior the annotations cannot: 'Every QR code using it renders with the new look,' disclosing the cascading, multi-object impact of the edit. It does not, however, say whether the change is reversible, whether omitted fields are preserved, or how quickly re-rendering propagates.

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, zero padding: the mutation is front-loaded and the consequence follows immediately. Nothing is repeated from the title or the schema, and both sentences earn their place.

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 nested-object mutation with no output schema, the description covers purpose, the whole-spec replacement semantics, and the cross-object render impact. It stops short of stating the return payload, whether id/name updates are partial-merge or replacement, or any plan restriction (which is buried in the nested schema instead).

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?

Top-level schema description coverage is only 33% (id and name carry no description), so the description has to compensate. It partially does by mapping 'rename' to name and 'replace its spec' to spec, and by making clear the spec is substituted wholesale rather than merged. The deep spec semantics live in the schema's own nested description, not the tool description, so this stays at baseline.

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 states specific verbs and the resource: 'Rename a design or replace its spec.' That pairs the two mutation modes with the two writable fields and is clearly distinguishable from designs_create, designs_get, and designs_delete. It even states the downstream effect, which no sibling shares.

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 — an agent can infer this is the tool for modifying an existing design, and 'rename or replace spec' hints at the two supported cases. There is no explicit when-to-use guidance, no mention of when to prefer designs_create (for a fresh lookalike), and no prerequisites such as ownership or plan limits.

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