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

With no annotations, the description carries the full burden. It usefully discloses that lookups are scoped to the calling API key, which is real behavioral context an agent can't infer from the schema, but it says nothing about behavior when the id is missing, unknown, or owned by another key.

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 short sentence, front-loaded with the verb and resource, no filler. It is arguably too terse, but the terseness is a completeness problem rather than a structural one.

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?

A simple single-parameter read tool with no output schema needs little, and the scoping note helps. Still missing are the id format and the not-found/unauthorized behavior, which an agent would want before calling.

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 0%, so the description should compensate for the single 'id' parameter. It only says 'by id' and reveals nothing about the identifier's format or constraints, leaving the agent to guess at what a valid id looks like.

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 and resource ('Fetch one loop by id'), which clearly separates it from the siblings list_due (enumeration) and register_loop (creation). It doesn't name the siblings, but the single-item fetch intent is unmistakable.

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?

No when-to-use or when-not-to-use guidance, and no mention of list_due as the alternative for discovery. The phrase 'for the calling API key' hints at a scoping constraint but doesn't tell the agent when this tool is the right choice.

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