Line9

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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: the auth requirement, the hard boundary that this connector cannot publish or save, and most importantly the identity-stamping behavior of the `line9:` frontmatter that must be preserved to avoid creating a duplicate diagram on publish.

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?

Purpose is front-loaded in the first sentence, and the follow-on sentences earn their place by covering the frontmatter contract, auth, and publish boundary. It is somewhat dense with workflow/CLI tangents, but there is little redundancy.

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 tool with an output schema (which the description correctly does not duplicate), the definition covers the auth prerequisite, prohibited actions, and the crucial frontmatter-preservation rule an agent needs to act correctly. Nothing material is missing.

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%, so the single `diagram` parameter is fully documented by the schema (name, slug, or trailing public_ref). The description merely echoes 'by name or slug', adding no new meaning and actually omitting the public_ref option the schema lists, so the baseline 3 applies.

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 first sentence gives a specific verb and resource: fetch a published diagram's Mermaid source by name or slug and show it rendered. That clearly separates it from list_diagrams, and implicitly from render_diagram (fetch vs. render-a-given-source), though no sibling is named explicitly.

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 gives real context — Line9 sign-in is required, this connector cannot publish or save, and publishing happens in the Line9 web UI via open_url rather than the CLI. However, it never states when to choose get_diagram over render_diagram or list_diagrams, so tool-selection guidance is only implied.

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

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new context: it is scoped to the user's own workspace(s) and requires authentication, which annotations do not 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?

Two sentences, zero filler, with the resource and returned fields front-loaded and the routing guidance last. Every clause earns its place.

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 enumerating return fields is lightly redundant, but the auth prerequisite and workspace scoping fill the remaining gaps. Nothing an agent needs in order to invoke this correctly is missing.

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 description coverage is 100% – both 'limit' (range and default 50) and 'query' (case-insensitive substring) are fully documented in the schema. The description adds no parameter syntax or format detail beyond that, so the baseline of 3 applies.

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?

Specific verb (List) plus resource (diagrams) plus scope (published in the user's Line9 workspace(s)) and an enumeration of the returned fields. It explicitly routes to the sibling tool with 'find a diagram before `get_diagram`', so an agent can separate it from get_diagram and render_diagram immediately.

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 a clear use case ('find a diagram before `get_diagram`') and names the follow-up tool, plus a prerequisite ('Requires Line9 sign-in'). It stops short of stating when-not to use it (e.g., when the diagram id is already known), so it is strong but not fully explicit.

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

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), yet the description adds substantial independent context: no sign-in required, a Line9 watermark for non-Pro users, the inability to publish or save, the required source-side configuration, and the panel-vs-terminal reply behavior. This is exactly the value-add a description should provide on top of annotations.

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?

Purpose and the core call trigger are front-loaded, and most sentences carry actionable detail (error re-call loop, panel branching, publish limitation). It is dense and a few clauses could be trimmed, but almost nothing is padding.

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?

Despite an output schema existing, the description wisely explains the verdict shape (kind, size, warnings, parse error with line/column, plus open_url) because agent reply behavior depends on it. Combined with the panel/no-panel branching and publishing constraints, an agent has everything needed to call this correctly and handle the result.

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%, so both parameters are already documented, and the description's 'set it in the source, never as arguments' guidance largely restates the schema's own note on frontmatter. The `plan` parameter — including that it is a hint that may be skipped — is not addressed in the description at all, so baseline 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?

States a specific verb and resource ('Render Mermaid source with Line9's layout engine') and immediately scopes the behavior: flowcharts/sequence diagrams get Line9 layout, other kinds fall back to Mermaid's own layout and are flagged. An agent knows exactly what this produces and can distinguish it from the read-only siblings get_diagram/list_diagrams.

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?

Explicit trigger ('Call this whenever you write or change Mermaid and the user should see the result') plus clear conditional handling: fix the named line on parse error and re-call, and branch replies by whether an MCP Apps panel exists. It does not, however, mention when to prefer the sibling tools get_diagram or list_diagrams, so sibling routing is left to inference.

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