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

With no annotations, the description carries the safety burden and does so: 'Read-only' is stated up front, the ±15% tolerance and deterministic sort order are disclosed, and it explicitly says an empty results array is a successful answer rather than an error. It does not discuss permissions or response size limits, keeping it short of a 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?

Front-loads read-only status, then purpose, then usage, then return behavior. Every sentence adds a fact the agent cannot get from the schema, and the alternative is placed at the end where it reads as a routing hint.

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 output schema exists, yet the description enumerates the response contents (matches, diameter, deviation percent, tolerance, catalog version) and interprets the empty-array case. For a two-parameter read tool this leaves no meaningful gap.

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%, so the baseline is 3, but the description adds genuine semantics: omitting threadIds scopes to the whole active catalog, and each selected thread is evaluated at 1, 2 and 3 threads per strand. That clarifies what the id list actually controls, which the schema alone does not.

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?

Opens with a specific verb and resource ('Finds catalog thread constructions') plus the exact matching rule (±15% of a target diameter). It is clearly distinguishable from calculate_rope_diameter, which is named as the single-thread alternative.

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?

States the triggering user question ('which threads to use for a rope of a given thickness') and offers the sibling alternative for the single-thread case. It also gives explicit branching on the optional param: omit threadIds for the whole catalog, pass ids to narrow.

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