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

Annotations already establish readOnly, non-destructive, closed-world behavior, so the bar is lower. The description adds genuine information beyond them by enumerating the returned content (factor-by-factor scores, fit rationale, entity, source URL), which matters because there is no output schema. It does not say what happens for an unknown 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?

One sentence, front-loaded with the resource, followed by a compact enumeration of outputs and the sourcing hint. No filler and nothing redundant with the schema.

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 single-parameter read with no output schema, the description covers what the tool returns and where the input comes from. The only gap is failure behavior for a missing or invalid signal id, which is minor at this complexity.

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% and the single parameter is self-documenting, so the baseline is 3. The description adds meaning by stating the id's provenance (from search_signals), though calling it `id` while the schema field is `signal_id` is a small naming mismatch an agent must reconcile.

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 in full" names the resource and its scope, and the colon list (score breakdown, fit rationale, entity, source URL) tells the agent exactly what comes back. It stops short of an explicit verb like "fetch"/"retrieve", but the contrast with the sibling list tool is still inferable.

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?

"Pass the `id` from search_signals" gives clear prerequisite/chaining guidance: search first, then fetch a single signal. No explicit when-not guidance or error-condition handling is offered, but for a one-param fetch tool the usage context is unambiguous.

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