index_update

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

Annotations declare idempotentHint=true, destructiveHint=false; the description goes further by explaining WHY it's safe: 'Safe to call after edits; existing chunks are reused by content hash.' This adds mechanism beyond the annotation, exactly what the lower bar rewards.

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 clauses, front-loaded with the action, then the safety guarantee, then the usage condition. 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?

No params, output schema exists so return values needn't be explained, and annotations cover the safety profile. The description adds the incremental/hash-reuse semantics and the trigger condition. Complete for an agent to invoke correctly.

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?

Zero parameters, so the schema provides nothing and the baseline is 4. The description correctly implies no inputs are needed (it operates on repository state), and adds the 'since the last run' semantics that define how the tool behaves without arguments.

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+resource ('Indexes files') plus the incremental scope ('that changed since the last run') and the secondary effect ('embeds the new chunks'). This distinguishes it from siblings like index_rebuild (full rebuild) and index_status (reporting).

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?

Explicit when-to-use: 'Use it when the repository has been modified and the index is stale.' Sibling index_rebuild exists but is not contrasted; still, the trigger condition is stated clearly enough to route the agent, so this lands at 5 as clear context.

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