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

Annotations only cover the safety profile (readOnly=false, destructive=false, openWorld=false). The description adds substantive behavioral context beyond that: instances remain linked and stay in sync with the symbol main and all other instances. It also implies the operation affects the currently selected page, a meaningful side-effect note. It doesn't describe failure modes if no page is selected, keeping it just short of 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?

Three tight sentences, front-loaded with the action and resource before the rationale. Every clause carries information — sync behavior, the reuse pattern, and the page-selection prerequisite — with no filler.

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 mutation tool with annotations covering safety and a fully-documented schema, the description supplies the missing behavioral context (linking/sync semantics) and the required prerequisite sequence (list_symbols, select_page). No output schema exists but the effect is well-enough implied; minor gap on error/precondition behavior when no page is selected.

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 symbolId, position, and targetPath thoroughly (including enum meanings and the before/after-selected target requirement). The description largely restates that the target is the CURRENT page and references list_symbols for symbolId, adding little beyond the schema. Baseline 3 applies.

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 (Add) and resource (a linked INSTANCE of an existing symbol) and explains the mechanism that makes it a distinct operation: it stays in sync with the symbol main and other instances. It clearly separates itself from add_section and promote_to_symbol by naming the reuse goal (one navbar/footer/CTA across pages).

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?

Provides explicit prerequisites and pointers — call list_symbols to get the symbolId and select_page to set the target page before invoking. It also frames the use case (reusing a shared element across pages) which implies when to choose this over other add options, though it does not explicitly contrast against add_section or insert_block.

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