Look up whether these failure signatures have been seen before

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

With no annotations provided, the description carries the full burden. It explicitly states the tool is read-only, 'Doesn't modify history', and identifies the local store path. It doesn't cover edge cases like missing history file, but the key behavioral guarantees are clearly disclosed.

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 tight sentences with no fluff. The first sentence front-loads the action and target store; the second adds usage context and an explicit pointer to the write alternative. Every phrase earns its 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 simple 2-parameter lookup tool with no output schema, the description covers purpose, usage, storage location, safety, and alternatives. It doesn't describe return format or edge cases, but the core context is sufficient for an agent to invoke it 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?

Schema coverage is 100% for both parameters, so the baseline is 3. The description adds a small connection between signatures and extract_failure_signal's FailureSignal entries, but mostly repeats what the schema already provides.

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 opens with a specific verb ('Look up') and a clear resource: a local history store of failure signatures for the repo. It clearly distinguishes itself from siblings by contrasting with record_triage_note, making the tool's unique role obvious.

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?

Explicitly states when to use it: to say 'this has happened N times before' instead of treating failures as novel. It also points to record_triage_note for persisting explanations, providing a clear alternative and exclusion.

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