nexus_index_build

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

The description says 'Build or refresh', which implies a state-changing/write operation. Yet the annotations declare readOnlyHint=true, which is a direct contradiction. This is a serious safety signal mismatch and fails to disclose the index mutation behavior.

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 two short sentences, immediately stating the action and its prerequisite. Every word earns its place; there is no fluff or repetition.

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 simple one-parameter tool, the description covers the key context: what it does, what it contains, and the required usage context. However, it does not mention return values or side effects, and the contradiction with readOnlyHint leaves a gap in safety context.

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 covers 100% of parameters, including a clear description for 'force' ('Force full rebuild (ignore incremental cache)'). The description adds no extra meaning beyond the schema, so the 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?

The description uses a specific verb phrase ('Build or refresh') and identifies the resource ('the code index') with contents ('symbols, imports, calls'). This clearly distinguishes it from sibling code-intel tools like nexus_file_symbols or nexus_references that consume the index.

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?

It explicitly states it is 'Required before code-intel tools,' giving clear when-to-use guidance. However, it does not mention when it might be unnecessary (e.g., if the index is already fresh) or provide alternative tools, so it's not a perfect 5.

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