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

With no annotations, the description carries the disclosure burden and does it well: it names auth requirements, explicitly says no inline credentials are accepted, and promises an actionable error when Jira is not configured. It also enumerates the returned fields. It does not explicitly state the absence of side effects or invalid-issue handling, but 'Fetch' plus the field list implies a read-only operation.

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?

Three focused sentences front-load the operation and example, then cover return values, auth, and error behavior. No filler words or redundant restatements of the tool name.

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 no output schema, this covers the full invocation contract: what is fetched, what fields come back, which credential is used, and what error occurs on misconfiguration. Nothing essential is missing for an agent to call 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?

The input schema already documents the only parameter with format and examples at 100% coverage, so baseline 3 applies. The description repeats the key example but adds no new parameter semantics beyond the schema.

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 'Fetch a single Jira issue by key', a specific verb-resource pair with a concrete example, and clearly differentiates this from siblings like jira_search or jira_create_issue by restricting to a single issue lookup.

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?

It states the intended use (retrieve one issue by key) and adds a meaningful constraint: the call relies on the caller's stored Jira credential and rejects inline credentials. It does not explicitly name alternative tools or state when not to use it, so it stops short of full routing guidance.

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