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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: it spells out the shape of the returned Markdown (lanes, ordered messages, notes, sections, full request/response payloads), which matters because there is no output schema.

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 tight sentences: the first front-loads what the tool does and what it returns, the second covers inputs. The enumeration of output fields is long but earns its place since no output schema exists to carry that information.

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 read-only, two-parameter tool with no output schema, the description covers purpose, output shape, and input modes adequately. The only meaningful gap is routing guidance relative to the many sibling tools that also operate on diagrams.

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%, and the schema already explains that id is 'used instead of source'. The description restates the same source-or-id alternatives without adding syntax, format, or mutual-exclusivity detail, 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?

The description gives a specific verb ('Read ... as Markdown') and resource ('a Volley diagram'), then enumerates exactly what the output contains (lanes, ordered messages with numbers, notes, sections, payloads). This clearly separates it from an SVG producer like render_svg, but it never names check_diagram, verify_diagram, or get_diagram, so sibling differentiation is left implicit.

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 two input modes ('Pass source text or the id of a saved diagram'), which implies when the tool is usable, but it gives no guidance on when to prefer this over verify_diagram, check_diagram, or render_svg, nor any exclusions or prerequisites.

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