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

Annotations already cover the read-only/idempotent/non-destructive profile, but the description goes well beyond that: it discloses the auth requirement, the hard capability limit (no publish or save), the side-effect-free nature of edits unless the line9: frontmatter is preserved, and the identity-stamping consequence of dropping that block. This is exactly the kind of mutation-adjacent context annotations cannot express.

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?

Front-loaded with the core action, then layered with the frontmatter warning and capability limits; every sentence carries information relevant to calling it correctly. It is dense but not padded, though the CLI aside is slightly tangential to the call itself.

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?

With an output schema present, return values need not be explained, and the description still extends it by noting the rendered view and the open_url link. Auth, capability boundaries, and the identity-preservation caveat are all covered, leaving nothing an agent needs in order 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?

Only one parameter and schema description coverage is 100%, so the schema already documents 'name, slug, or trailing public_ref'. The description repeats 'by name or slug' but adds no format or resolution-order detail beyond the schema — baseline 3.

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 (fetch) and resource (a published diagram's Mermaid source) with both lookup modes (name or slug) and the rendering behavior. It is clear on its own, but it never names or distinguishes itself from the siblings list_diagrams and render_diagram, and 'show it rendered' arguably overlaps with render_diagram's territory.

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?

Gives real usage context: Line9 sign-in is required, the connector cannot publish or save, and the publish workflow is via the Line9 UI/open_url rather than the CLI. It stops short of routing between sibling tools (when to call this vs render_diagram vs list_diagrams), which keeps it out of the top band.

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