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

Annotations already declare readOnly=true, destructive=false, idempotent=false, openWorld=true, so the safety profile is covered. The description adds genuinely new context the annotations cannot convey: the BYOK credential model ('transit in-memory only, never stored') and the fact that descriptions are transformed to Markdown on return. It stops short of covering error behavior for invalid keys or missing permissions, which keeps it from 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?

Two sentences, front-loaded with the payload contents and followed by the security posture that an agent needs before handling credentials. No filler and nothing buried.

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?

An output schema exists, so return values need no explanation, and the description covers content plus the non-obvious BYOK auth requirement for a 4-required-parameter tool. The remaining hole is failure/edge behavior (invalid or inaccessible issue key) for an open-world remote fetch.

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% — every one of the 7 parameters, including the token/auth trio and the fields filter, is documented inline. The description restates the optional comment and attachment behavior but adds no defaults, formats, or constraints beyond the schema, so the baseline of 3 is appropriate.

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?

It names a specific verb and resource ('Fetch a complete Jira issue') and enumerates exactly what comes back: summary, Markdown-converted description, status, assignee, priority, labels, custom fields, plus optional comments and attachment metadata. What's missing is any explicit differentiation from siblings like search_jira_issues — an agent must infer the single-issue-by-key vs. search distinction from the field list.

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 never states when to reach for this tool versus search_jira_issues, nor does it tell the agent to obtain an issue_key via search first. The only implicit usage signal is the phrase 'optionally comments and attachment metadata', which hints at the two boolean flags rather than providing routing guidance.

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