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

The annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real value by disclosing the auth requirement (API key plus Signals layer), but it says nothing about behavior for a missing or invalid id.

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 short sentences, with the auth prerequisite front-loaded. The second sentence is telegraphic to the point of being cryptic, but nothing is padded.

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 one-parameter read tool with annotations and no output schema, the description covers auth and scope. It leaves the id format, the where-to-get-the-id flow, and the error behavior undocumented, which matters when the schema describes nothing.

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 description coverage is 0%, so the schema only declares `id` as a required string. The description says "by id" but adds no format, source, or example, so the agent gets no help distinguishing a slug from an opaque identifier.

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?

"One Signal by id" states the resource and the cardinality, which implicitly separates it from search_signals. However, it is a fragment without a verb, so an agent must infer that the operation is a single-record fetch.

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 description gives the prerequisite (an API key with the Signals layer) and implies "use when you already have an id." It never names search_signals as the alternative for resolving an id, and it states no exclusions.

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