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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: X-API-Key requirement, org-scoped visibility, and the important disclosure that unknown and other-org hashes both return EVENT_NOT_FOUND with the same message (guarding against hash enumeration). It also confirms nothing in the ledger is mutated.

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 and organized with clear 'When to use' / 'When NOT to use' markers, so navigation is fast. The trailing inventory of return fields is mildly verbose, though defensible given there is no output schema.

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 no output schema, the description compensates by listing the returned fields (event_hash, event_type, event_seq, public_* mirrors, hash_valid, agent_chain_valid, trust_level, trust_label, proof_anchor_status_label, chain metadata). Combined with auth, scoping, and error semantics, an agent has everything needed 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?

Schema coverage is 100% and the single parameter's description already states the 64-char hex format and its source tools. The description repeats the same provenance, so it adds little semantic value beyond the schema; 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?

States a specific verb (fetch) and resource (public proof payload for one ledger event) plus the keying parameter (64-char hex event_hash). An agent can immediately distinguish this read tool from siblings like list_my_recent_decisions and log_decision/log_outcome.

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?

Explicitly enumerates when to use (after log_decision/log_outcome, when trust labels, chain validity, anchor status, or a paired-event proof URL are needed) and when not to use (browsing many decisions, writing events), naming the concrete alternative path: list_my_recent_decisions then get_proof on a chosen hash.

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