evaluate_external_store_performance

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

With no annotations, the description carries the burden of behavioral disclosure. It does add specific context about what it detects (selector reference instability, concurrency bypasses), which goes beyond a generic 'analyze' statement. However, it does not mention whether the tool is read-only, whether it has performance implications, or what it does with the profile path. For a profiling/analysis tool, some of this is implied, but the transparency is only partial.

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 description is a single, focused sentence with no unnecessary words. It front-loads the action ('Analyzes') and specifies the target resource and key outcomes, earning every word.

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?

Given the tool's moderate complexity (2 params, no output schema), the description covers the 'what' and 'why' but does not explicitly describe the return value or report structure. However, the tool name and phrasing ('identifying') imply it returns an analysis result. For a simple analysis tool, this is mostly complete, but the missing output format slightly reduces completeness.

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?

The schema description coverage is 100%, so the baseline is 3. The description adds no additional meaning to the parameters beyond what the schema already provides. The parameters are well-documented in the schema, so the description correctly relies on that.

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 clearly states the tool's specific purpose: analyzing useSyncExternalStore performance and identifying selector reference instability and concurrency bypasses. This verb+resource construction distinguishes it from sibling tools like get_render_summary or find_spurious_renders, which target broader rendering issues.

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?

The context is clear: this tool is for when you need to evaluate useSyncExternalStore performance and detect specific issues like selector instability or main-thread blocking. However, it does not explicitly mention alternatives or exclusions, such as 'use get_render_summary for general rendering issues' or 'not for non-external-store problems.' The implied usage is evident but not fully explicit.

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