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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: every tools/call result carries a signed second content block when signing is configured, which tells the agent where signatures come from and when they exist.

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 concrete return payload before the usage rationale. Dense but every clause (PEM + JWK, canonical format, offline verification, signed second block, HTTP mirror) carries information; only the HTTP endpoint mention is arguably secondary.

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?

No output schema exists, so the description must convey the return value, and it does (PEM + JWK key plus canonical signing format). With annotations covering the safety profile and no parameters to document, an agent has enough to call and use it correctly; a brief note on key rotation or cache lifetime would make it fully complete.

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 tool takes zero parameters, so baseline is 4 per the rubric. The description correctly implies no inputs are needed and instead describes the returned key formats, which is the relevant information here.

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+resource: returns the ECDSA P-256 public key (PEM + JWK) plus the canonical signing format. An agent can immediately distinguish it from siblings like system.verify and the many workflow.run_* tools, since it is the only key-material provider.

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 the purpose-driven context for use: verifying signed tool responses offline without calling back to TradingCalc, and notes the alternate access path GET /api/mcp/pubkey. It does not explicitly name system.verify as a complementary/alternative tool, so it stops short of a full when/when-not routing statement.

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